Believe I have an extra "front" of engine "breastplate" (#30 on diagram) that I can send you. (I also have #11 and one not shown on other side - check to see if they are needed). There probably is the carb filter heat stack hole (blue) that would require a can lid to block off. The 2 big holes (red - ones at either end) are for air from the shroud. #58 and 44 are missing too but are not critical to cooling.
I talked you dad into buying a bag of stainless steel button head bolts for the engine tin - hopefully they are in his stash. They work well for the engine tin.
I'm off on ocean cruise in a week but back by March 1 (if no Coronavirus!). So just let me know address and I'll get it to you (I'm NW FL).