Power/torque issues

Howdy, I've been restoring my jeep for 4 years and I'm having issues in providing enough power/torque to make my 4th and 5th gears usable on the highway hills without tearing up my transmission. What I mean by this is that once I hit 4th gear I could floor it (not on the hills) and my speed only crawls up and once I gain enough speed to go into 5th gear and I shift it into 5th. The speed just remains constant as it was in 4th. With the top speed only being 55-60 mph

My tire size is 33"

I've replaced my distributor with an HGI my tuning is great I've got and AMC 20 in the rear. I'm wondering if I should replace my rear diff gears
or if I should replace my stock carb. If you have any other suggestions let me know. All input will be appreciated thank you.

-Mike

How about we start with, "what gears are in your diffs now?" and "What engine/w carb do you have now?"

GEARS, GEARS, GEARS. I know a few Jeep owners that can not even use 5th gear any more once they install larger tires. My guess is you probably have 2:73 differential gears. You might want to start looking at 4:11 gears. I have a 5.3L Vortex w/300 hp in mine and I have the same issue. My 4:11 gears are on the way. All the power in the world want help without the right gears.

Engine: 258 4.2L
Carb: stock 2- barrel on the small size
Gears: I've put new in but I can't recall what the ratio is. I know it's a non slip diff but the ratios I'd have to check on.

Thank you for your input I believe it is in fact the gears.

Should I go ahead and put in a new carb as well? If so what?

I appreciate the input, sorry for the late response.

A good friend of mine and a member of this forum has a stock 4.2L with a Weber carb and headers that runs excellent yet he still can't use 5th gear because of his gear ratio.