The 65 truck has rear coil springs and all the related suspension attachments welded to the housing. Those would have to be removed and new spring perches welded to match your 58.
You would probably have to do some surgery on the later rear axle as well providing it isn't too wide.
I have been running a 350 in my 56 with a 3sp OD trans and the stock 390 rear end since 2000. I don't think you can break the stock rear end with that combination, the main problem is that it is probably geared too low for suitable highway driving. A better ratio rear end or an overdrive of some type would definitely help.
Fred
Last edited by rfs56trk; 09/12/2014 9:54 PM.
