Need help with the 3.7L

Based on your symptoms, I would start looking at the fuel system. Any car this old will be subject to problems there.
- Rust or crud in the fuel tank can be clogging the fuel filter. This will become more evident as the fuel flow increases at the higher engine power levels needed for higher speeds. Change the filter but expect to have to pull and drain and clean the tank. Any car of this age seriously needs to have the tank cleaned and inspected.
- Rotted rubber fuel lines from the tank to the main metal fuel line under the car or from that line into the fuel pump. These can crack and allow air to be sucked into the fuel supply and limit fuel flow in that manner.
- Old fuel pump failing and falling on its face, that will starve the enigne of fuel.

Did you get all of the old gas out of the tank when you got the car? If not, then if the gas iss indeed old and 'varnished up', then that can get in the engines valve guides, cause them to stick, and that can bend pushrods. So, that is another reason to pull the tank and clean it all out and inspect it.