A 235 and 261(same looking block and mounts) will bolt in, good idea to run 'til it dies, while looking for full oiler. 230-250-292 are 3+- inches longer, not as easy to fit. If you do the original brakes, king pin bushings, tighten up the steering, etc, will learn a lot, not cost much, be much easier to drive. Several disk brake conversions out there, can save for later. Power booster doesn't make it stop any better, just easier to push on pedal.

'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.