TC for 904.?

Your welcome. The converter for 68 and up transmissions is real popular. If your just looking for a stock converter Makko sells them for about $100. That'd be the way to go because it sounds like you have the old style converter that not only has less splines but they had a smaller crankshaft register (the button on the front that slips into the crank) so in addition to the price of them changing the insides you'd need to buy an adapter ring. By the end you'd have a lot into a stock converter, as much or more than an entry level performance converter would cost.

LOL... They sure don't know torqueflite's saying a 727 won't fit behind a small block. The only time you run into a balance issue with a small block torqueflite is on a late 340 (late 72 thru 73) or if using it on a 360 as they were externally balanced. All others are internal balance and need no special torque converter.

That's correct on a non-lockup input shaft. Here's a picture of them both. The top pic is a lockup, bottom isn't