Here's some pics of interest. My engine as of the work I completed tonight:
So I did a final put together and my bolt up fan bangs against the crank and thermostat housing, when I use a spare stock fan, it works great but puts me over budget on the radiator when I do a final measurement. So I answer my own question and if anyone ever changes from a 6 to a 350 it won't matter and worst case you have to get a spacer for your fan to get closer to the radiator, but if you change from a 350 to an inline you must use the 6 cyl frame brackets and move the engine back for radiator clearance.
So thank you after all locdoc for the 6 cyl brackets. They weren't what I was looking for in the beginning, but something I needed in the end!
hoggyrubber, why do you need to replace the passenger side? Is it cracked or not lining up? The frame mounts may have changed in 67-72, from 63-66 I dunno... I know the block mounts were the same, I got mine off a 66 model, sorry I didn't notice what location the frame brackets were in, but come to think of it, the frame mounts were there, so if we decide that is what you need I can get it for you easy and cheap from that same truck. To answer your question yes, my V8 used the front holes, but you will need to use the rear holes for Rad clearance like me....
Just for the heck of it here is a pic with BOTH the 6cyl and the V8 Frame brackets installed in their correct locations at the same time. Note the different lower bolt location so there is no moving them around. This is looking at the passenger side so the left bracket is the V8 and the right is the 6 Cyl.
