Congratulations on a successful transplant. 3700 is still a high RPM for cruise. If you anticipate long cruise trips, an OD transmission such as NP-540 series, Clark with an O in the MN, Advance Adapters, I believe, makes an OD unit that bolts in front of main trans. These and most similar units bolt right in with shortening of the driveshaft required.

Ed

Last edited by EdPruss; 08/25/2023 9:34 PM.
'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.