Here's a follow-up on my split exhaust manifold as seen in previous posts on this thread.
After cutting, trimming and fitting a pair of stock cast iron manifolds, I had my welder friend do his thing and assemble all the pieces. We first preheated everything using a propane cooker stand. I ordered Mike some good high-nickel rod and after welding we let it cool down real slow overnight with fiberglass insulation wrap and moving blankets. After that I had the pieces media blasted and applied hight temp cast iron colored paint that was cured in the kitchen oven. Then I mocked-up the install with a stock intake mounted on my spare engine. With these in place I could fab up a 2 to 1 headpipe.
More pics of the exhaust manifold build:

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1975 Dodge D100 225 c.i., HEI, Parallel Offenhauser, Motorcraft 2150, 904 auto, 9.25" 3.55:1

Inspired by Reed in his post on the same subject viewtopic.php?f=44&t=66712 I set out to make my own split plenum intake manifold using the same process. Rather than a steel divider, I chose to use some 1/4" aluminum that I had. First thing was to make a tool rest for my jigsaw. I cut and drilled to allow for mounting the plate solidly to the Offenhauser intake while I cut slots for the divider through the larger hole. after doing one side, I flipped the plate around and cut the other side. Because of the plenum's shallow interior, the jigsaw blade was shortened to allow for unobstructed operation. I used files and sandpaper to fine-tune the fit and cut out the divider after making a cardboard template. The interior fit's pretty good and the divider height is a couple thousandths proud to allow for clamping down with the carb spacer/adapter and gasket. I don't think it'll move around much, if at all. Once I get my new head installed, I'm looking forward to running with and without the divider in place to test its impact on performance.
Pics of the divider fab:

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1975 Dodge D100 225 c.i., HEI, Parallel Offenhauser, Motorcraft 2150, 904 auto, 9.25" 3.55:1