I have used adjustable locating pins when installing a Tremic transmission behind a 455 Pontiac. It wasn't too bad getting them inline, toughest part was rotating the engine with the dial indicator on the crank. Once the bell housing was centered, I moved the indicator to face of the housing for the second adjustment. This is were the shim stock comes in handy. Once the second adjustment is correct, the first needs rechecked. The dowel pins worked really good, key is marking each reading at every 45 degrees, then study on it before adjusting. The Pontiac came out dead centered and parallel with the crank after a few hours of work. I used shim washer for the parallel adjustment, https://www.mcmaster.com/products/shim-washers/ring-shim-sets/

Joe