I have a 1978 Mercury Monarch that has acceleration issues w

I have a 1978 Mercury Monarch that has acceleration issues when going up hills. What can it be?
I have a 1978 Mercury Monarch that has a straight six under the hood. I live in the Seattle area so there are lots of hills. The car drives good when on pretty level ground, but when going up a hill my car struggles halfway up the hill struggling to speed up. Is it an exhaust leek issue, a motor issue, or a fuel mixture issue? I changed my carb two weeks ago and put in new spark plugs. there's no engine knocking or sound coming from under the hood. If you may help me with this issue and tell me on steps to take I'll be thankful.

A bit more info and some testing results could certainly be useful.
since you have put those parts on, has there been any change at all?What's the exhaust back pressure at 2000rpm? Anything over two psi indicates a restriction in the exhaust
Has the timing advance mechanisms been checked for correct operation?What about basics how much compression does the engine produce, and are all the cylinders inside 20% of each other if it generates enough?It should have about 125# of compression anything less than 90# indicates SURPRISE. a worn out engine.
If all else fails, or if you want to use up your money in a more proper manner TAKE IT TO A PROFESSIONAL PERFORMANCE TECHNICIAN..

ASE Mastertech

sounds like you have to replace your fuel filter.

Its old. purchase a new car.

check the timing, it may not be advancing like it should

Does a 78 Monarch have a catalytic converter? If it does, have it checked out.

If the ceramic converter honeycomb is smashed, the debris can shift under load and block the exhaust, causing a steep acceleration drop off.

Fuel filter, or fuel pump. I had a '76 Monarch, and the reverse happened, I goed up Snoqualmi Pass, going up hills did good, going down it choked and sputering, got to the top okay, but going down the other side, it died. Had to replace the fuel pump. But, I'd attempt the fuel filter 1st.