First, this is a big tractor trailer truck motorhome conversion website, so you won't necessarily get the best info for a question on mini-trucks.
I believe the 5-speed used in your 95 is an integral bellhousing style, and has different bolt pattern than the 4.3. You need a 4.3 pattern (same as Chevy v8) transmission. Earlier models had separate bellhousing, but I am pretty sure your year is integral.
With all the hassles, it would be better to just get a used 2.2 junkyard take-out engine and swap that in place of your junk 2.2.
2005 Kenworth Showhauler 45 ft total length
twin screw, 450 hp ISX, 10 speed Ultrashift