well here's a couple'a pieces of info that I hope will help ya out.
I did a 305 in mine outta an old parisienne pont. I had kickin around.
A company named "transdapt" makes the motor mount arm kit as far as the rear tranny mount I just used the original one outta the parisienne & drilled some new holes in it to match up to the frame width. used a mid 70's dodge d-100 truck rad cuz the rad hoses location on the orig. rad wouldn't work out. just have to narrow the opening in the rad support a bit, I just used I piece of sheetmetal to do this. also used a aftermkt. flexfan as I thought the orig. clutchfan stuck out a bit too far.
...The driveshaft ....well I just wandered around the wrecking yard with a measuring tape, til I came across one the right length, mine is a short box truck (well it was at the time, it's now got a panel body on it) found the shaft in back of a van with a whole raft of S-10 parts in it so I gotta assume its outta an old s-truck then just used adapter universal joint on the rear end, the front end plugged right into the splines on the trannie
shifting is looked after by an automatic column outta a 57 fairlaine just had to lengthen it a wee bit, 1/2 inch or so. (nothing looks worse than a modern column/steering wheel on any vintage vehicle, many of these columns & wheels were works of art on their own)
mine is the 700R4 4 speed auto. with 3:50 rear gears, works just dandy, with the economy cam & jetted down quadrajet carb & 235 75 15's truck gets around the 30 mpg highway. (tho you ain't likely to get that outta a 350.
Whilst you're at it you may as well upgrade to pwr. dual action brakes, I used a booster & master outta a 88ish dodge 150 this is practically a bolt on item, you only need to slot the truck's original master cyl holes a wee but,& on the one I used even the orig push rod was the right length there is a bit of hyd fitting adapting to get the br. lite switch to hook up to the brass brake block & of coars you gotta lengthen the wires down to the frame.
s'all I can think of for now, hope you can glean some info from it.
Mikie
near Ottawa Canada
57 merc 100 panel & 64 econoline p/u