We need some more information (the first 4 characters of your VIN, i.e. U19T) to say for sure. I'm in the reassembly stage of putting a 12-valve hemi 3G83 engine (which was the standard for early-to-late 90s U42T minicabs) into my '90 U19T which had a dead non-hemi, 6-valve 3g83 in it. I think it's a difference of 4 or 5hp, from 37 to 41 or so, and I am installing the 5 speed in place of the 4 (4wd). The thread is here: https://minitrucktalk.com/threads/u42-12v-5mt-4wd-into-u19t-6v-4mt-4wd.22781/ But the gist of it so far is that using the old engine/trans mounts on the newer engine will work with a little bit of grinding. I'll be reconnecting the intake/exhaust/cooling/fuel this week so I'll know more on that soon.
Getting warmer! If you have a 3G83, you can do the swap I'm working on (fingers crossed!) for about a 10% increase in power. If it's the 3G81 or older, it is possible but uncertain. If you're serious about pursuing it we can exchange some critical dimensions and try to get a better idea. What I'd love to do is see a 4A30 and a 3G83 side by side on a bench and see if that unit could be put into a fourth-gen minicab (U11 through U19) without welding.
Ok! Let's compare blocks. I have lined up the left (rear) face of this 3G83 block with the 5" mark on the craft board. We're looking at the intake side, which faces up at you when you lift the seats. The big hole left of center is where the oil filter arm goes, and directly below it are two holes on the same plane at about the 8.625" mark: those are for the upper engine mount. Are yours in the same place? Also, follow that mount to where it attaches to the frame. It will bolt onto another little pillar that is welded to a sled kind of thing. Mine is made of 1-1/2" or so pipe, is yours?
