62bigwindow. I'm not sure what camshaft, cubic inch displacement, or compression ratio factors you've got with your engine. You indicated that the camshaft duration is 236 degrees @ .050.
John Mummert has a Y-284-S cam listing that shows 236 degrees @ .050. That Mummert listing also shows an advertised duration of 284 degrees, a 108 degree lobe separation angle, and a 68 degree intake and exhaust valve overlap. These are numbers I equate with top end performance not street-ability drive-ability.
IF JM's Y-284-S cam listing is akin to what you have in your engine, I suspect that the low end engine torque is marginal for stop-and-go level terrain driving and may be exasperated by start-up on any significant incline. My suspicion is that your 4.09:1 rear gears make low speed performance of your '56 wagon workable and support low speed drive-ability.
Other variables may come in to play with what you're experiencing in the drive-ability of your '56 wagon. My hobbyist experience tells me that a given aftermarket performance camshaft will exhibit very different drive-ability performance in a 272 cubic inch y-block than it does in a .060 over-bored 312 (322). Similarly, the effective operation of a performance camshaft is tied to an engine's static compression ratio and the dynamic compression ratio the engine actually operates with on the street.
Accomplishing street-ability with a high performance engine while dropping engine speed for highway use is a challenge. Your T-85 R-11 overdrive offers a .72:1 final drive ratio with a 2.49:1 first gear. Consider looking at a TREMEC Super Duty T-5 part no. MD 552-0251 from Modern DriveLine. 5th gear final drive ratio is .63:1 with a 2.95:1 first gear. I think this transmission would work better for your application with either a 3.73:1 or 3.56:1 rear end because it has a lower 1st gear ratio and a higher final drive ratio than the T-85 offers.
Hope this helps!
NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York