They are very different. On foxes, the bellhousing is shorter and the headers wrap around that so 87-93 long tubes will not fit with the 94-95 bellhousing. I have 87-93 headers on mine and I had to change to a fox bellhousing, input shaft, and also had to massage the mid pipe a bit to fit the 87-93's. Also, when you do that much, the transmission is moved forward an inch so the shifter hits the shifter bezel and I had to move the whole drivetrain back an inch with my QA1 K-member.
Yes and no. If you run a aftermarket K-member and a 351w it will work no problem but with the 302 depending on the transmission you may have problems. Although with all ford transmission I have never had a problem only with a TH-400.
Yes, They are different and YES they WILL fit with some MODIFICATION!
If you run a fox style clutch fork/bellhousing/transmission setup they will slip in no problem. I put bbk's on mine and all I had to do was take off the old exhaust, steering shaft and a valve cover. Didn't have to jack the engine up at all, just slipped right in. I had converted to a tko and had to use a fox style clutch fork and bell.
On the issue of moving the engine back, that is TOTALLY NOT needed. They make driveshaft spacers for this sort of situation and steeda sells one specifically for putting a fox style trans in an sn95 body, and it costs all of 60 dollars.
So unless you go about switching this stuff (not worth it for another t-5) then they will not fit, but if you want a transmission that will survive a whole hell of a lot of BEATING, then go for it.
You don't run into problems relating to driveshaft length while running a fox tranny and bellhousing, but if you have a short shifter, like many of us do, the shifter moves forward about an inch and in my experience, my hand would slam the center console on the 2 to 3 shift.