Yes, your machine shop can drill the crank flange to mount the V8 flywheel.
With a 3.08 differential you would be wise to use the 3.11 low gear, which gives you the 2.2 second. If you plan to haul loads or pull a trailer with that combination, then the 3.50 might be a better choice. You might also think of adding an overdrive from a Saginaw three-speed to your 2.54 transmission, which would allow you to run a 4.11 or lower differential with a higher ratio available for cruising on the highway. See
http://www.chevytrucks.org/tech/overdrive.htm i have no knowledge of what kind of abuse the T-5 can absorb, but i hope soon to find out what the Saginaw's capacity may be.
In my '52 Chevrolet two-door we have a 3.11 Saginaw four-speed with an overdrive conversion and 4.88 posi differential. In overdrive the final ratio should be 3.42. For most purposes i plan to use the 2.2 second as the "low" gear, duplicating the old "close-ratio" three speed. (This vehicle is not a "daily driver" . . . especially on $3.00 gasoline.) At some point, after we have seen what this machine can do, we may install a 3.36 differential and use the 3.11 low gear. That might be a good combination for you in your truck.
God's Peace to you.
d
Inliner #1450