I'm sorry, but I can't let this go. For as beautiful as it is, you do realize that you don't have the right engine in it. The H-M-built Grand National stock cars ran 430s with a heavy-duty 3-speed stick-shift transmission from a '59 Mercury. Find a built-up model of a '58-'60 or '61-'67 Lincoln and use the 430 from it. AMT reissued the '66-'7 Lincoln Continental Convertible back in the '90s that can be used as well. It looks like you found a 3-speed transmission, but if someone else is wanting to model it they use one from a late '50s-early '60s Ford car/truck or Mercury, scratch-build one or modify one from a non-FoMoCo car as well.
BTW the story of the Beauchamp/Petty controversy was told to me by an old mechanic from western Iowa who used to be Beauchamp's crew chief when I was researching my first T-bird history book in the early '90s. He pulled out a scrap book covering Beauchamp's career from dirt tracks in the Midwest through the end of his driving career, including several articles from the Omaha World-Herald about the lead-up to the race and the days afterwards. I wanted to run the story about how he got short-changed because of Petty's wife's conflict of interest in being the official lap-counter, and how the Good-Old-Boy system (Beauchamp was an outsider because he wasn't from the South) also played a factor, but my editor nixed mention of it out of fear that the France and Petty empires would sue them for defamation of character, etc. After I heard this story and did some more research I gave up watching NASCAR and put it in the same league as professional wrestling (which the World-Herald would always refer to as "rassling" in a pointed jab at how matches were pre-determined for their entertainment value).