| Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | Your highway speeds are determined by rear axle ratio, right now if you have a two speed rear axle, your speeds are slow and slower, so you need to change your rear axle. No rear axles with that bolt pattern are available, get a modern rear axle with that bolt pattern.
270 and 292 are about the same length, however the updraft carb and associated manifold would be hard to make happen on the 292. An OD trans. will solve your highway speed problem, if you have enough power to pull it.
Where in CO are you located.
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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