With 153 tooth flexplate, a straight line starter goes with it. A long mounting bolt and short mounting bolt.
With 168 tooth flexplate, a staggered starter goes with it. Both mounting bolts are long.
Sometimes you will get a starter where the mounting has been surfaced. One can shim the outer bolt only to move the pinion into the ring gear. Shim both bolts equally to move the starter away from the ring gear.
You can just buy the starter nose piece from the dealer, and use the new starter guts.
Don't forget to bolt up the end support strap to the starter. This helps supports the other end of the starter and prevents it from cracking when used.
Others may chime in here to add their suggestions.