http://www.ebay.com/itm/400570953608?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

Well I found out this radiator will fit my '59 f100 without much modification. Move the mounting ears backward, a bit of trimming and drill new mount holes, that's it! Looks like it may even take the stock hoses. Keep in mind this will be a daily driver and will be expected to tow a small 5th wheel. Big rad is a prerequisite

But what to do about the cap? Stock on these trucks is 7psi and the 75-85 E vans take a 13psi. Should I split the difference or go with a 13? I already have a 195 T stat installed.

I would stay with the 7 UNLESS you have replaced the heater core and even than I would probably stay with the 7.13 puts extra pressure on the whole system including head gaskets etc.

  

Good point. I do plan on replacing the heater core as well. One for an early '90's Ford Exploder reportedly works in the '57-60 F series with minor mods (Murray 398001). But head gaskets is another concern even though this is a reman motor from a reputable rebuilder.

Assuming the rest of your coolant system is in good shape, you should be good with a 13 lb. cap on the newer radiator. It was the large expansion tanks on the earlier radiators that necessitated the lower pressure caps. As Mark brings up, a higher rated cap will put additional stress on the heater core and various gaskets.

Lorena, Texas (South of Waco)