i have a 1976 dodge 3 speed PU, it has a Slant 6 in it and i seem to have a major power fall off in 3rd gear climbing hills

Welcome to the world of "Small engine in large vehicle". Why not down shift to 2nd?

Are the valves adjusted correctly (says the guy who runs them tighter than stock).
Done a tune up lately?
How are the filters (air, fuel).
Is your truck a half ton or 3/4 ton?

We could use a little more detail here.

Oh yeah, welcome aboard!

Hello and welcome! What Eric says about small engines in large vehicles is true. I have a 1986 Dodge Ram with a 225. Thats a 5300+ pound vehicle being motivated by a 225 cubic inch engine with 100 horsepower.

Easy fix- do like Eric recommended, shift into second.

Complex and/or expensive fix- starting upgrading carb, cams, ignition, etc...

Is this power loss new? What are the specs of your engine? ONe barrel? Two barrel? Have you done any changes to the engine recently?

What kind of gears have you got, and what is your timing set at. Incorrect timing can be a major pain.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

i dont know the gears on the transmission, and the timing was re done, the carb is a 2 barrel Carter. I have power now, i rebuilt the carburator yesterday, there was a flooded float, and a bunch of grime in the carb, i blew it out with compressed air. also the automatic choke was reversed