seems to me the compressor instructions specified the quantity. With R134 you use PAG oil.

 

PAG oil and R12 oil don't like each other, but Ester oil is compatible with both - more expensive, but easier to use. I tend to use it when converting, just so that I don't have to be as diligent flushing and changing components (swapping to 134a but not changing the compressor, etc.).

Brackets to switch to a Sanden-style are fairly common and cheap, eBay has a pretty good selection - just beware of how your mount works as far as a belt tightener, there are some options. Fittings-wise, you can get quite a few different options on either one, Tube-O, Rotolock, Flange, manifold, etc. Usually just match 'em up to what you have, and away you go -

 

It didn't come with instructions and I would expect it to use more or less depending on the size of the system.


I flushed the condenser and evaporator very thoroughly, flushed the small line from the condenser to the txv. A new txv made for 134 was installed, new high and low side hoses were made to fit.

I have searched and searched and can find very little info. Every thread I read about 134 retrofits leaves out how much oil was used and most leave out refrigerant charge. Best I was able to find was 8oz of oil and 28oz of r12. Since the system is going to be 134, I reduced that to 22.4 oz initial charge estimate. I am starting to wonder if I am over on my oil level. I charged today and cannot achieve vent temps lower than 78 degrees. I consitantly have low pressures on the high and low sides. Adding refrigerant does not seem to change this.I shot the evap with an infared thermometer and it only shows 59*f. I am at a loss at this moment. I clamped off the heater lines to make sure that I didn't have hot air leaking in. No change. I realize the condenser could be causing some of the issues, as it is not a parallel flow, but several others seem to have gotten vent temps in the 50s.

 

I converted to the sanden-type years ago. I just fabricated the bracket. I recently had to put an all new system on it because the compressor was R22, and the lines were rotted. In the process, I managed to drill a hole through the coil as I was putting everything back together. I eventually a new one that goes in a mustang for much cheaper than stock. It required a little work to make it fit.

 

https://www.sanden.com/objects/Compr...structions.pdf

According to Sanden you drain the old compressor, measure how much you got out, then replace with that much in the new one.... BUT they say the new compressors come pre-filled and do not require that.

On their web site Sanden USA it says you should use SP-15 oil (Sanden's part number 7803-1996.)

Do a search for "R134 refrigerant capacity chart 1974 Ford" and you only get 339,00 hits.

The above took maybe a minute and a half.

 

Oddly, you may have too much R134 - try bleeding off some and see if your temps improve.

 

I made a mistake treating the compressor like any other ac job I have done. Most compressors on the shelf at autozone or like like, I drain and add oil per the manufacturers spec. Unfortunately my compressor did not come with instructions. Now as far as the refrigerant capacity goes, Did you open a single link that it brought up? I have found one result on google, that lead me back to this site, stating 28oz. Believe me, I have searched until I am blue in the face, hence my post here. Everything that was brought up either skipped the year or said see under hood decal. I get the fact that repetitive posts get old, but people come here for info, not to be chastised because you feel they didn't do a search. I have been on this forum for close to 15 years off and on, when I see something I can answer, I'll help, whether or not there are 100 of the same post.

 

I made a mistake treating the compressor like any other ac job I have done. Most compressors on the shelf at autozone or the like, I drain and add oil per the manufacturers spec. Unfortunately my compressor did not come with instructions.

Now as far as the refrigerant capacity goes, Did you open a single link that it brought up? I have found one result on google, that lead me back to this site, stating 28oz. Believe me, I have searched until I am blue in the face, hence my post here. Everything that was brought up either skipped the year or said see under hood decal. I get the fact that repetitive posts get old, but people come here for info, not to be chastised because you feel they didn't do a search. I have been on this forum for close to 15 years off and on, when I see something I can answer, I'll help, whether or not there are 100 of the same post.

 

Couple of suggestions:
http://www.m-m-s.com/ackits_public/f...capacities.pdf shows Motorcraft capacities in R134. Only goes back to 1983 but you could use its suggestion of 33 oz as a starting point.
https://hychill.com.au/content/3-inf...doc-120201.pdf is an aftermarket coolant which shows 30% of the original capacity as 250 grams... from that a little math says 832.5 gr, about 29-30oz.
Ford Light Truck Refrigerant and oil capacity charts || TechChoice Parts goes back only to 85 but it shows a whopping 48 ounces original capacity R12. Since R134 is lighter by volume I'm told you multiply R12 charges by about 75-80% to get an R134 charge, which brings that 48 down to about 36-38 ounces.

No matter what, the 28 looks a little light. Think in your shoes I would add about 36 ounces and see how it performs. Bleed a little off and see if it gets cooler, basically just tune from there. R134, at least in our cars, is pretty picly about the weight - in the sweet spot it cools really well, but just a touch too much or too little, its efficiency plummets. Bleeding off maybe a couple ounces lowered the vent temp in the wife's car 10 degrees.

Congratulations on 15 years on the forums. Lord knows how many duplicate posts you must have seen by now.