I was wondering what the big differences are between the 94 7.3 turbo IDI and the First gen 7.3 powerstrokes? always wondered, never found out.

 

A lot.

The Powerstroke is a "computer controlled" engine.
Direct injection
Much more complicated and expensive to repair.
Faster out-of-the-box, flat out more power.
Plug-n-play capability, you can upgrade the power by/through the computer. That has its hazzards though as you could melt the pistons out of you motor without even expecting it.
Injectors fire with a complicated (in my opinion) oil/hydraulic system.

The IDI gets its name from the InDirect Injection. There is a prechamber in the head where combustion begins and the injector puts the fuel there. The P.S. injects the fuel directly into the main (and only) combustion chamber.

The IDI is a "mechanical" motor, everything runs with out computer input which makes it much simpler and easy for the home mechanic to work on. No scan tools needed.
The injectors simply "pop-off" when they recieve enough fuel pressure from the injection pump (IP). You can buy a whole set of IDI injectors for the cost of one P.S. injector.
Parts for IDIs are very similar to the cost of parts for gas motors only they are usually heavier duty. For instance most gaskets are the same price and a rebuillt IP is not much, if any, more expensive than a good carburator. Check out the price of a set of valve cover gaskets for a P.S., you'll choke. I just bought some for my IDI(Fel-Pro, not cheapies) for $9.99!
You can fairly easily (as far as I'm concerned) build an IDI turbo that will run with factory Powerstrokes, Duramaxes and Cummins. But if they modify their truck you'll be left in the dust again. A '94-up Cummins for instance is so easy to get mo' power out of it's rediculous.

The P.S. was a necessary evil, the old mechanical motors had a hard time meeting ever increasing emissions laws. The old Stanadyne IP the IDIs had wasn't quite precise enough. Dodge and Cummins had to upgrade from the older Bosch VE rotory IP to the much more expensive Bosch P7100 in-line IP to meet newer emissions stds. too. But they finally had to go to a Computer controlled IP/motor in mid '98 as well.

If you like/have to work on your own rig the IDIs win hands down. If you take your truck to the dealership you might want to go P.S. (I'd go Cummins myself) there aren't many mechanics that know IDIs anymore especially at the dealerships.

 

Not saying all are like this, but way to many mechanics today are lost if the computer don't tell them what part to change.

Since there is no computer, 1/2 of the mechanics out there are lost before they even start on an IDI.

 

The only mechanic I use is a really GREAT MECHANIC not just a parts swapper like most are today but even he knows very little about IDIs. He knows more about P.S.
He's a GM guy so he knows a little about 6.2 and 6.5 GM diesels and a lot of that crosses over to the IDIs.

 

what about the block? was there any difference in the bell housing bolt pattern?

 

Block's not the same BUT the bolt pattern IS.