904 converter missmatch

65 Dartman said

What year is your car? That would possibly explain why you're having problems. If your car (or the engine is a 67 and earlier) it takes the small converter hub. 68 and newer engines take a converter with a larger hub. Additionally, the converters will not interchange frpom pre-67 to post-68 because the spline count in the front pump is different. That would explain why your old converter fits the crankshaft but does not fit the new transmission. Hope this helps.

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After some research i have figured that out too, i thought it would work since i have an engine block from around mid 70´s, but it looks like there is an older crankshaft in the engine, perhaps from the same engine where my -66 heads originate from.
But my questions remain, can i get it to fit in any way?
Can i grind down the converter hub to the smaller size?

Edit car specs:
-76 318 block with hydraulic lifters, Cast: 4006730-318-4
-67 heads, Cast: 2658920-3
340 cam, no idea of year.