I totally agree with the thinking of making it as you want. These cars do not appear they will ever be worth the numbers older 'muscle' cars still bring, with the exception of ultra low mileage originals that potentially bring low $20's - at most. BTW, the M21 4 speed option means it came with a Borg Warner Super T-10. Many (many) people have thought over the years that the M21 option meant it came with a Muncie M-21 transmission. I guess that was GM just confusing everyone back then.