Not sure about MPH but the 28" should change the 60' due to the roll out difference I believe . Been awhile since I've raced and had to figure any of this out .
I'm planning on setting mine around 32 total timing , right now i'm at about 27 TT . Where did I get my numbers , just reading on the net . Don't know they're right but I'll try it
If you have enough compression to run the cam you have listed then I think you need more carburetor . See if you can borrow a couple different carbs from buddies and go out and do test and tune .