Here is some more information for anyone that cares to chime in.
This first pictures shows the mounting brackets for the Delco CS121 61Amp alternator that is installed on our '88 MJ 2.5L no a/c pickup.
You can see there is no adjustment that would allow something larger to be installed.
These next two pictures are of the original alternator and the '96 Buick Roadmaster that fits Benjy_26's 87 2.5L no a/c truck.
On-line research says the '96 Buick Roadmaster's alternator is a CS144, (144mm diameter frame)
My calls to the local alternator rebuilder says both the '87 and '88 MJ should use the same alternator.
That agrees with Autozone and Napa counter jockeys that tell me its a Delco CS121, (121mm diameter frame)
There is also a CS130, (130mm diameter frame) that is supposedly as common as field mice in GM cars.
The ear hole to ear hole spacing on my CS121 is 6.170" which agrees with info I found on-line.
The ear hole to ear hole spacing on the CS144 is 7.200"
Some websites say the CS130 is the same as the CS144, but many more say it's 6.600"
Most pictures of the CS130 are with the ears not directly opposing each other but offset.
Perhaps these offset ears match the dimension of the CS121? (of course then I'd need a longer serpentine belt)
Does anybody have dimensional information?