I'm looking for the plate that blocks off the cross over pipe inlet on the right side manifold for a dual exhaust set up, 1964 394 engine, Dynamic 88. I'm converting single exhaust to duals. I could try to fabricate something, probably not hard, but if the actual part is available I'd prefer that.

 

I'm interested in this question as well...tagged for interest

 

You're going to start a bidding war for the one that comes available!

 

I think there was an OE cap available. This would be handy for a concours restoration. As mentioned, if this cap becomes available it's probably as rare as hen's teeth.

Don't forget that you could remove the exhaust manifold and have the crossover welded shut. @Oldsguy had the exhaust manifold on his 69 Delta 88 modified this way.

 

I can't recall what shape and thickness those block off plates are. If you make one for passenger side, wouldn't you need to make one for the drivers side to eliminate the crossover pipe ?
All you should need is 3/8: or 1/2" thick cold rolled steel. You can fabricate a gasket if you have a leak,

 

Buy a quality flange that fits your manifold
Such as ... Walker Exhaust Flanges - Free Shipping on Orders Over $109 at Summit Racing
weld a disco into that and now you have what you need

 

Grabbed this pic off an eBay listing (not mine). As a few guys here mentioned, seems like a pretty easy fix to make up a steel block-off plate to fit this application.

 

Get a piece of 1/8 thick steel plate .
Using the gasket as a guide, cut a three cornered piece .
Round the sharp corners off, then drill 3 holes, again using the gasket as a guide.
Use a regular flat exhaust gasket between the plate and the manifold.