| Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | When considering a 420 swap, measure input shaft stick out, OD and count of splines, retainer dia., mounting bolt pattern, they all need to match up, whether they do now or when you modify a 420, it doesn't matter. A good idea to do.
Ed
'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.
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