If you'd like an idea as to what's involved in a Trooper diesel re-power, read this thread and also have a look at the link in my signature.

I can't comment on how (dis)similar the 1987 and 1988 Trooper frames are, or whether the 1987 has the hydraulic clutch release like the 1988+ models. Other members will be able to clear this up, I am sure.

I am guessing the diesel engine you are interested in is the same 2.8l that I have, which will not bolt to any gas Trooper transmission that I know of (there is a photo on my site showing the differences in the bellhousings). I do not know whether the 1987 has the same transmission as the 1988, but I am fairly certain you will need the diesel transmission too.

As far as other modifications go, read over my project pages and feel free to ask any questions you may have. It is rather more complicated than simply bolting it in, but not impossible.

Off the top of my head, you will need to address/replace the starter, cooling system (radiator and all hoses, incl. heater hoses), clutch lines, throttle cable, exhaust, driveshafts, engine/transmission (obviously), fuel system (except the tank; everything else needs modifications), electrical wiring, gauges (if you desire a tachometer and sedimenter warning lamp), vacuum system, and add a glow plug system of some sort. Not meant to be an exhaustive list, of course...