73 Duster wont handle

FYI:

Slant six with Air got 318 bars, 340 bars are not much beefier. If the car sways around you need to make sure all the suspension parts are up to spec, an alignment on a car with a bad part will not help much. A slant six is easlily within 50lbs of a small block with an aluminum intake manifold and headers. No difference in handling after a motor swap. In Fact the stronger engine should make the car handle better when powering out of a corner.

I started doing my own alignments about 25 yrs ago and can adjust the car to do what I want it to do. Caster can be set without a gauge if need be. These cars have eccentric washers/cams and can be adjusted with a wrench and socket. Moving the rear upper a-arm eccentric will change your caster, if you move the eccentric so the rear of the A-arm moves towards the engine you will increase caster. This usually does little to camber. Check your toe in before and after adjustment, minor caster adjustments will not change much if any sometimes. If the car pulls to one side you need to either increase caster on the side it pulls too or decrease caster on the side it pulls away from. Can do this by trial and error. Too much positive camber makes the car wiggy too, especially on roads with allot of tracking worn into them from big trucks.

These cars are bad about wandering if the caster is minimal or negative. Bad tires can cause pulling and wander too.

I shoot for 1/16 positive toe in. Read up on it, front end alignment is easy once you figure out the basics, then you won't have to pay for a mis-alignment any more.