Hi all, haven't been on here in a while, good to be back. Ok I need the advice of you collector car guys out there. This weekend I am picking up my dream car, a fully restored 1970 Mustang Mach 1 with the 351 4v Cleveland engine (original) and FMX automatic transmission. I need some insight on what. the old car crowd is running in these old flat tappet engines. This one has been all rebuilt to original specs with all Ford parts. It's the original 11:1 compression and runs terrific. I've always been the Mobil 1 guy and am thinking of running 10W30 or 10W40 high mileage oil in it. thoughts or input from experience? I appreciate all replies and apologies for the long post!