What would a knock from flywheel on 360 tell you?

[Mo Power]

Well I'm considering buying a 360 that my cousin sold to a kid that is in a 80 Dodge Ram and he says theres like a knocking around in flywheel area and I don't see how a flywheel could knock unless lose or torqued to much.And it's a 78 block and what tranny would it have 727 or 904? Also could someone verify what exactly the difference it between those 2 trannys.

[Charger1970]

I had a similar problem on a GMC once. The bolts holding the flex plate to the converter were loose. 

[John_Kunkel]

Possible knocks from flywheel area:

Loose converter bolts
Loose flexplate bolts
Cracked/broken flexplate
Crankshaft thrust bearing worn and allowing converter bolts to hit back of block

A 360 truck will have a 727 which is physically larger than the 904.