Would a 71 383/727 have a 10" or 11" converter bolt pattern?

I have a factory 71 383/727 from a 71 Satellite and I want to order a new a converter but I am unsure of which bolt pattern this set up uses. I searched but it seems that there are a lot of variables and I wasn't able to find a definitive answer. The combo is altogether and in the car so it's a little hard to measure accurately. The motor was a 2 barrel motor if that makes a difference. The auto parts stores show both flexplates for the year and model. Thanks

with out a looky see, no telling what is has been done to it since 1971.

all that is need is the correct size stock flex plate to install what ever size TC you want.

with a external balance TC you want the correct weight on the TC.

for example, I used an external balance TC from a 400 B engine on my external balance CAST CRANK 440.

IIRC, 383/400/440 cast crank share the same weight on TC.

I keep a few small & large flex plates for swaping TC around as needed. they all interchange and are 2 sizes.

IIRC,remove dust cover and you may tell by the starter ring gear, if it is thin it is the large TC and if it is thick it is the small TC

Thanks for the reply. I am 98% sure that the 383/727 is all stock because my Dad bought the car new and it had not been modded previously but it sounds like I need to pull the cover and take a look anyway. I have restored a good number of GM muscle cars but this is my first time doing a Mopar so I haven't come across a lot of these issues before. From searching it seems that if the 383 is a cast crank motor it will be externally balanced and a forged crank would be internal--correct? If it's externally balanced the weight will be on the converter correct? Thanks

A '71 383-2 would have an 11 3/4" (12") converter with the 11" bolt circle.

2-barrel motor would very likely have a cast crank so be aware that external weight might be needed.

what John said.

and yes, yes.

I checked the balancer and it looks to be symmetrical all the way around on both sides and does not look like the external balanced units that I saw when I searched online. I pulled the inspection cover on the trans and it definitely has the larger converter but I do not see any weights on the converter so maybe I got lucky with a forged crank. I searched online and the pics I found showed the balance weight on flexplate side of the converter and the one I have only has 4 tabs welded on it for the flexplate mounting bolts. Anything else I should check? Thanks for the help.

I think you got it.

happy wrenching.

RE: cast crank motors

Sounds like you are owner of a non-molested car, that's great. The engine ID pad on top front of the motor will have a bunch of numbers/letters stamped into it. For example, I think your engine ID should start out with G383. If the engine was built with a cast crank there will be an "E" stamped into that pad, either at the end of the number or sometimes off by itself. There may be other markings too. This engine ID tells how the engine was actually built. This information is easily found online.

For example, it could have undersize rod and/or main bearings or an oversize lifter, all from the factory.

R.