Help please

I just installed some new clifford headers and intake with a lokar throttle and kickdown cable.
It's a slant six 1972 duster. It started with no problems multiple times. I figured I'd take it for a spin before getting started in the exhaust.

Backed it out of my parking spot. And the when changing gears it shook a great amount and shifting is a problem. You really have to slam it to move into park or drive or whatever you put it in.

I put it in drive and it died and now won't start or even turn over.