There isn't any trans with OD that will fit behind a flathead and clear the crossmember. You need to define "highway speeds", 60 - 65 on rural highways is do-able with just lower rear gears. If you want to go 75 in traffic then you need major upgrades to brakes, suspension, etc.

RSWhitmore, I'd be curious how you hooked up a clutch linkage? Are you using hanging pedals?

 

Another good point, I guess I would be content with 55-65mph which the C4 did fine when it was in my F100. Definitely dont want to have to upgrade the suspension, etc.

Thank you all, giving me a lot to think about and learned a few things.

Update: all my front end (fenders, hood, etc.) are off being media blasted.

 

I killed myself hunting for that unicorn. The short answer T-5... crossmember is "not frame" while also being frame - it provides torsional strength (frame twist when 1 wheel goes into a ditch etc).

T-5 is really the best current trans option at the moment.

here's a complete list of what I have figured out will go (verified by users who did the actual swap whenever possible):
Ford F1 series Transmissions swap


The thing that has me curios to those who did a ford SB (289/302/351w) with a T-5 which T-5 did you use, the chevy 350mt pattern from a S-10 or a ford pattern from a mustang (and then a total tail section swap).

 

It really isn't that big a deal. Just cut out the original transmission cross member. and bolt in a new one for the T5. That's probably the easiest modification I did. The independent front suspension, new rear suspension, and mid 80's 9" rear end was more work, but the transmission cross member was easy. The overdrive will definitely be worth the effort.

 

Yes, a stock Mustang GT pedal assembly. Cut off the top bracket and fabricate one that will bolt to the under side of the dash. Also bolts to the firewall with master cylinder and booster on the other side, just like in a mustang. I used a Mustang GT booster and a Cobra master cylinder(with two outlets instead of the three used on the GT).

 

I used a T% out of an 89 Mustang GT with the mustang tail section. I used bucket seats, a short throw shifter, and a custom bent billet aluminum shift lever.

 

The typical T5 rear crossmember is just sized to support the trans. The original crossmember maintains fore-aft alignment of the frame rails, keeps the rails from twisting, and is the anchor point for the cab.

 

Will a borg Warner R10 from a '53 pick up, ford car work? I have one in my '53 and it has .70 final ratio, works with my stock 3.92 Dana 44 ok.

 

The R10 would be ideal, except it sits right where the crossmember in a 48-52 is. The solenoid is pointed right at the place where the brake pedal and MC are. You "could" do it if you cut the crossmember even more than for a T5, and went to hanging pedals. Lots of work.

 

Thank you for the link, it has great information.

 

This the primary reason why I don't want mess with the frame, I want to keep the integrity of the frame. I also feel it will hold its value better in the future, not that I plan to sell but you never know. The C4 with the flatty is looking really attractive. I found the adapter kit for the C4/flatty from Speedway for about $399 and wouldn't require mods to frame. Of course I giving up the OD.

 

With a C4, you could run as low a rear axle ratio as 3.25, the torque converter would make up for some of the low end loss. I would recommend the Flat-O-Matic conversion over the Speedway kit, not based on personal experience but on hundreds of good reports on their products. The Flat-o-Matic

 

I will take a look at it. Have used or heard of anyone using the Lokar 32inch Shifter from Speedway on the C4. I'm curious if it will align to the original shifter plate/hole.

 

Any reason you aren't considering an AOD with that adapter instead of a c4? My 66 F100 I had was great driving with the AOD. Just curious since you keep mentioning having overdrive.

 

AODs don't clear the stock crossmember, the C4 does.