My 74 145 pulls slightly to the left. All tires rotated around, all brakes/bearings checked, toe-in played with and set to 0".

I'm thinking that slightly more caster on the front left might straighten it out, that is, one more thin shim under the upper a-arm rear shaft bolt. Is this a good place to start?

I've also heard that adjustment with this means is a bad idea altogether, that it stresses the shaft or bolts excessively, and that fron suspension adjustments should be made between the crossmember and the body. How would that change just one side, by bending the crossmember?

Caster is applied to self centre wheels, but road crown makes wheels pull to kerb so that side is given more caster to compensate, usually .5-1 degree if your car is not sagging springs would be ok. Thousands of used springs are fitted every day with very low failure rates, bad roads,shocks,suspensions would cause most failures. Regards Jack.

Without proper alignment equipment it is all guesstimate. You can get it close by adding shim to area mentioned, camber will move only slightly but toe will have to be rechecked. Before you do any thing swap front tyres side to side if pull varies it is tyres if not it is alingment. Rear wheel drive should have some toe in, rolling motion causes them to toe out. You can make track guage out of old bonnet tow mirrors substituting four inch nails for mirrors. scribe line around centre of tyre and measure as close to centre as you can, then keep close eye on wear pattern, that will tell you a lot. Camber and toe affect wear caster does not. Regards Jack McIntyre.

Would a worn spring cause a slight pull? My thought is that after years of single driver operation, the spring gets slightly more worn on the drivers side, causing a little dip on that side and maybe a tendency to pull. I'd rather not adjust to compensate for that, but maybe it would make things a bit more balanced if I do change springs.

I've heard it is unwise to swap springs to different positions, that they will crack due to changed lateral stresses from the mounts. Is that true or only in very heavy vehicles?

Thanks. You seem to know alignment stuff really well.

If you have to adjust both sides an equal amount you can shim the
crossmember but if you only have to adjust one side you do it on
the A-frame. That is the standard, manual-recommended (and only reasonable)
way to do it. Note that doing that also affects the camber and the
toe-in. That is why you check and adjust the caster first, then the
camber and finally the toe-in.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma