I don't know about swapping, but hands-down I would opt for the 3.0. I had an '88 and the thing was a bit of a nightmare to get running right with the finnicky carb, and then a cracked head.

I've had two 3.0's, my second I just purchased with almost 160k on it, and it runs like a top. If you have the time and the mechanical inclination, maybe a 2.6 would be good for you, but I can't see it ever being preferable over the 3.0, provided you can find one.

My two cents (no actual redeemable value).

Third times a charm.