Torque converter/flexplate on cast crank 340

[Not A Duster]

I know almost nothing about automatics, and I can't seem to find this information anywhere.

Are all A904 Torque converters equipped with the 10" boltpattern? or do they vary?

I have a cast-crank 340 that I am putting a stock A904 trans behind as a temporary measure. The engine is externally balanced unique from other cast crank small blocks, so it needs a special "weighted" torque converter or flexplate.

B&M shows two flexplates for the cast-crank 340 on their website, one for the A904 & one for the A727:

http://www.bmracing.com/index.php?id=products&sid=3&cat=7&subcat=20

Now here's where I get confused: The Flexplate for the A904 is 10" bolt pattern only, yet they say:

"All Chrysler flexplates have dual bolt pattern (10" & 11-1/8") except #10231 & flexplates for A-904 transmissions."

K.....but what that does not tell me is does a stock A904 always come with a 10" bolt pattern torque converter? Local trans shop guy says that's not the case & I can't find such a specification in any of my manuals...Also: What would be the difference between B&M's 904/727 plates other than the bolt pattern??

I would hate to spend $120.00 on a flexplate that won't bolt up to my trans. And I'm not currently interested in buying a new converter.

Thanks in advance.

 

[Locomotion]

The 727 flexplate has 3 different bolt patterns to cover just about everything and has a larger overall diameter. The 904 flexplate has 2 bolt patterns and has a smaller diameter. The only difference is the extra pattern on the 727 within the extra diameter. They include 5/16" and 7/16" holes.

I have used the 727 flexplates with a 904 without a problem. But some people have had a clearance problem with some older Mopar mini starters. I'm not sure about the larger OEM starters.

Do you have the 904 converter yet? If so, measure first.