Flex plate to convertor gap

Hello all,
Really need in a bit of advice here, I have a 3/8" gap from flexplate to convertor. From internet hunting that seems too much. Car originally a 64 273 and 904 combo. I installed a 71 318. Using 318 flexplate, and original TC from 273.
I'm stuck between using a "Spacer Washer", or pulling motor back out. But still not sure what my problem is if I do pull engine. Maybe replace flexplate? I feel like using a spacer is just masking another problem.
I did use the Pat Blias bushing in engine for smaller snout on convertor, and it slides/spins freely. But is pulling it out 3/8" too far? Don't want it to disengage from trans pump.
Any advice???

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