The dual Mopar powerglide pattern isn’t that big of a deal now. ATI and others offer some great products and in seconds you can switch your ATI case to powerglide, small block Mopar, or big block Mopar. If you are building any power you are pushing a stock 50 year old powerglide case so why not build some safety into your race program.
Having dual bolt patterns on the block is just adding unneeded complexity IMO. Everything needed to put a glide behind a stock style Mopar block is a phone call away.
I understand what you are saying, But, if you are at a multiday race and blow the tranny, with a dual pattern you could conceivably borrow your buddies chevy reid cased transmission and be back in the race..
Having dual bolt patterns on the block is just adding unneeded complexity IMO. Everything needed to put a glide behind a stock style Mopar block is a phone call away. 
