I noticed there are a few different centerforce part numbers which one do I need I have a 69 350 block with a 400 crank it's a 383 I'm not sure how it was balanced when built I got it used for free any help?

 

Gotta know how it's balanced.

If it's the stock 400 balance it'll need one FW; if it's the 305/350 balance it'll need another. Without knowing how your motor is balanced, no way I (or anyone else) can tell you which one you need. We'd have basically a 50/50 shot.

You might look at what's on it now and get the same type setup, if the current one doesn't vibe.

 

So I have the harmonic balancer is on it as well as the original flexplate as it came is there a way of telling based off that?

 

If the original flex plate ran right, without vibes, then whatever balance that has, is the flywheel you should buy.

Hopefully it hasn't been "custom" hacked on, a common BAD thing that happens when people screw up and allow their damper and flex plate or flywheel to EXIST in the same shop at the same time with their rotating assy.

 

If the flex plate has weights then its externally balance or if completely smooth on both sides its internally balance

 

ask me how I know , I learnd the hard way sorry I just noctice this was old