Mike,there are 6 bolts. The 700r4 will just slip right in. I just replaced my 350,and got lucky. I didn't have to change the drive shaft. 350's come in 3 lengths 27 11/16,30 11/16,and 37 7/8. The 700r4 comes 28 3/4, 33 27/32,and 37 7/8.
I am using 1985 Camero 305/700r4 in my 39 Chevy coupe and they both were the 37 7/8.As for as getting to the top two bolts,I lowered the tail shat with a jack to get a little more room. Remove them first,then support the engine before removing lower four bolts.
Hope this helps.