yeah, you need A balancer and A flywheel or flexplate when balancing, but if you have to grind on either of them to get it to balance, you have other issues- at least that's the way my machinist explained it to me when i got my 355 all machined up 4 years ago. since i put the engine together and installed it in the Nova, i swapped from an auto with the flexplate that was used for the balance job to a 4 speed with a brand new GM flywheel, and it doesn't vibrate all the way up to 7200 rpm. that flexplate ended up in my 92 Caprice cop car when it's stock flexplate broke, and is now in my 88 S10 with that very same Caprice TBI 350- and it doesn't vibrate on that engine.
maybe i might get the Eagle 383 kit and a brand new LT1 balancer, and get the balance checked out locally- which is probably a good idea, anyways, given the care that some people put into mass produced items these days...
you don't plan sincerity.
you have to make it up on the spot.
wanna hear about 20 years ago when i was too smart to know any better?