Josh, I had a 3.50 first gear 4spd Saginaw in Joy's 51 truck when I built it 7 years ago. Low gear was too low for my tastes with a 235 and 3.40 rear end gears.It should be ok with a 2.73 or 3.08 rear gear. I still have the tranny collecting dust in my barn.I then installed a 2.85 first gear 3 spd Saginaw,slightly doggy on take off but pulling the 1400 lbs travel trailer was no problem at all.With the 261 in the truck now , the 4 spd OD A883 trans and the same 3.40 rear, it ok with the 3.09 first gear.
Bolts right up to a 48 and leater truck clutch housing, 21 inches long like all GM car trannys. I use swap meet Hurst shifters, modify the mounting bracket to move the shifter as close as possible to the main case, cut and weld the shifter rods to fit.Then make up a shift handle, bend it suit the situation. Speedo driven gears are easy to get from the various Camaro after market sites.
Pull the tranny apart, generally the spring washer on the mainshaft between first gear and the rear bearing is flattened,resulting in too much main shaft play.The shaft walks back and forth beating up on the bearings.I throw the feeble spring washer away and shim the gear using king pin shims or what ever.The input bearing is also usually worn, you can buy the bearings cheaper at a bearing distributer than the rip off prices on some websites and auto parts stores.Las Vegas Driveline is a good source of reasonably priced syncros if ya need them.
Some say they break easily,GM used them behind 300 hp or less. I know guys with built small blocks abusing Saginaws with no problems.
