Water Jacket Cover Rust Holes

Thank you both for your suggestions.  I'm looking into both.

See if Doug Prey has at Auburn Cord Duesenberg Parts Company in Broken Arrow, OK - I know he has two sizes in stock, though not sure if that is a years thing or a cylinder thing - very nice reporoductions too and reasonably priced

I would braze the areas that are convenient, then coat with POR15

Regarding my 1929 Auburn 680 Engine, the stamped steel water jacket cover has 5 or 6 rusted through holes at the bottom radius between the flat section and the stamped/raised section.  They range from pin-head size to a couple 1/2" long slits.  It's been stripped of paint,  cleaned and treated with POR-15 etching solution and has 2 coats of POR-15 coating.  I was planning to smear some JB Weld Steel Reinforced Epoxy over the holes and pitted areas, then paint the inside surface with Glyptal.  My friend, who has restored many antique Ford tractors,  questioned whether that would hold up.

Should I:
1). Continue what I was planning?  Or,
2). Use my CNC machine to fabricate an aluminum part?  (I built a 4'X4' CNC primarily for woodworking, but it is capable of milling aluminum and I have done so several times with shallow cuts.)  Milling steel on my machine is out of the question.  I would use 1/2" thick aluminum and hog out the under-side in a rectangular cross section for the water to flow under it.

I prefer to do Option 1 if it will hold up.