We may need to know more info.  Do you want to keep the T90/Dana18 combo behind the V6 or would you settle for a whole different train?  If were going to do anything like this, I think I would opt for something modern with fuel injection set up.  I do like the 4.3L GM motor.  I dont think there would be any suspension issue to change, that 134 is a heavy sucker but you would have to do some frame mods.

Putting in a V6 is not an easy swap. You also need better brakes and higher ratio axle gears. The 5.38 gears are to low for anything over 45-50 mph.

Yes, sell the Jeep and buy a later model that would suit your needs. Leave the old girl stock.

Phil,
I think thats what we're trying to say, that there isn't really an easy way to do this, or a specific donor car that is going to give you the outcome your looking for in a fast easy way.  You may want to talk to the guys on the 2A page for more info, they have a group that did some cool mods and would have some insight, Rocnroll did a really nice one, but it took him 6 years and almost wore him out, His words.

There are so many options that you can use, it all depends on what you want when your done.  Bottom line is that your making a vehicle go 60 mph that was designed to go 40mph.  Its going to need some suspension mods in order to safely be what you want it to be.

Just sayin
Todd

Well, i'll throw my 2 cents onto this old thread.  The amount of work to swap just about any motor, with the exception of a straight 6, will be about the same.  From my experience, there is almost no difference between installing a 4.3 or any any of the small block Chevy V8's.  The D18 will take them all and the T90 is good up to a 327-if you are a sane driver.  From an axle gears standpoint, the 5.38's will work but an OD is necessary to get the greatest benefit.  4.27's with the OD would work very well with these engines (I'm using 4.10's).

It has also been my experience that the mileage from any of these GM swaps is always about the same and in every case is better than the 134.  While the 9" brakes and Ross steering leave something to be desired, if in good condition and properly adjusted, they will suffice.  You will also want to make sure the rest of the front end is completely up to snuff.  Death wobble at 75 mph is probably just that.