I'd say you need a PTO pump more than anything
Isolator would be a good idea so you don't kill both batteries.
I think you would be better off picking up a PTO pump as well. by the time you buy a second battery and isolator it won't be cheap.
I might still have a second battery tray that will fit a 80-96 ford full size truck. It was out of an 87 diesel, and I had it my bronco. PM me if you want to look for it, It is buried in snow, I think I know where it would be.
(I have never run an isolator between my batteries, I have a marine style dual battery switch which really just makes it convenient, I have run a pair of optima red tops for years without any issues, I got them as a pair and plan to replace them as a pair. You should run an isolator though...)
Also you should look into an alternator upgrade. do a search for Taurus alternator in Bronco. it requires fabbing up a bracket and depending on what alt you have (if it is about 92 or older) it is probably not very high output. my 87 bronco came with a whopping 85 amp alternator.
Nathan
99 xj with stuff
build thread
http://www.rme4x4.com/showthread.php?83436-Nathan-and-Tanja-s-99-XJ-Build-up
