Just get the tubular crossover type. Nearly same for motor as for trans. Easy to do, adjustable and no welding(unless you want to.) Common method. Your TH350 will be just fine. Been there done that. Those "Engineering" shops are high dollar sometimes and you don't need fancy. If you can weld and want "special" mounts, go for it. But 350/350 is standard swap.

CLICK these.

http://www.classicparts.com/1947-59-V-8-Crossmember/productinfo/79-405/#.V7ZsC-n6s5s

http://www.classicparts.com/1941-59-Transmission-Crossmember/productinfo/79-505/#.V7ZsH-n6s5s

http://www.classicparts.com/1947-72-Front-Motor-Mounts-pair/productinfo/79-015/#.V7ZsWen6s5s

http://www.classicparts.com/1941-81...d-Shift/productinfo/79-208/#.V7Zss-n6s5s

TOTAL about $130

Axle ratio: Non overdrive trans have final ratio 1:1
Check your diff ratio. Stamped on ring gear. Stock would be 3.90 or 4.11. ouch!
You do not need to change the diff ratio unless there is something you don't like about acceleration or highway speed after swap. All depends on what kind of use the truck gets. You will have to get your driveshaft modified for this swap. Proper front yoke and length probably. Pretty cheap at a good ol boy shop.

P.S. I have reported Beltfed's Off Topic Hijack to AAA, KOA and NASCAR.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn