Sweet!!!! Sound like nice fellas!
RUSTYes, Fieros rust. It's pretty common and I can't imagine doing any reading and not finding a reference. Good news is that it's often either surface rust or hidden from view. (means you don't need to be tidy).
If the floor is solid and you are confined to the rear area you should be fine. If the rails and strut area are BAD then toss the frame and get another (no biggie) The battery area and the sides of the trunk are first to show. Get up under the liner and see the frame rail (I'll put up a pic or two). Is it rusty or is it gone (finger poke thru). This ties the 'box' where the motor and cradle are to the passenger compartment. You can weld in metal box sections to fix as they don't show. Heck I'll start a rust thread.
3800 s/c or n/a Okay you want one and can't see 20k$ Now don't get me wrong, you could easily drop that into it. Here's what you need: guys add in what I forget
1. non rusty space frame and cradle
Yes you may need some fixes The car is old.
2. 3800 motor DOH! Carparts.com or your fav wrecker. The work is the same for s/c or n/a and yes the innards are different. stock about 240 hp vs 215-220 hp, but lots more fun in s/c form. Ask Dan. Also the puter and harness.
3. Tranny....I have a 4 speed but the easy way is to use the donor auto. The auto is a faster drag car hands down.
4. Mounts... need to mount the front of the motor and a new dogbone. Dan adds a side mount and relocated alt bracket (nice stuff). Tranny needs some mods to bolt in (new holes).
Axle work for auto or clutch and flywheel for manual.
5.Wiring...Scary stuff but break it down wire by wire and it looks doable. Dan has done or almost done 4.
5 A OOPS! forgot you need an exhaust system. Needs to be custom made.
6. Time and tools... DIY and save have someone else do it and pay. (pm for info) Mine has only taken 14 months or so so far
7. Shit eatin' grin...take a test drive.
Yes there are other things. You'll want to upgrade or fix things that you may never have such good access to again. Poly susp, brakes, etc.
Gary