If you are going with the shafts you have you may want to groove them. Just make sure you go over the groove with scotchbrite or 600 grit emery cloth to make sure there are no rough edges. I had the good Isky rockers so I had them bushed and blueprinted by RAS. They have very nice shafts too but they are about $100 each. I think the spacers and good holdowns are a good idea.I got my studs and holdowns from Mancini and the spacers from Harlan Sharp.
I think you should be OK as long as you stay away from huge spring pressures twocents

Gus beer

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64 Plymouth Savoy
493 Indy EZ's by Nick at Compu-Flow
5-Speed Richmond faceplate Liberty box
Dana 60