I just replaced my motor after a rebuild in my 1995 F150 with the 4.9l in-line 6. All the vacuum lines are good and replaced anyways. The trucks fires up fine and the rpm at idle is solid but the engine seems to shake. The motor mounts are solid too. When I give the truck gas and the rpms go up the shake goes away and it’s no longer there. The truck also is a snail up hills and any wind will make the truck drive extremely slow. Any input is well appreciated thank you.

I am not sure if the plug gap but they were swapped right over with the engine and the base timing is at 10 degrees. The gears were not replaced but they were in very decent shape and I took them off and cleaned all of that up. I purchased a timing light and set the timing and I know it’s at the 10 degree mark. The distributor was not replaced but was cleaned up. All new plug wires too.