That was my reasoning for asking. I am pretty sure my motor is date coded as a late '66 (ok, so it's not the orig, '68 motor! you all got me ). I assumed it was a 390GT block. The person working on my car went to change the oil pan and said it has a windage tray so I need another gasket.
A windage tray fits around the crankshaft throws to prevent crankshaft wind currents from aerating the oil.
It is also wise to use the deep sump pan to get the oil further away from the crank throws to help resist oil frothing
Without the tray the the crank wind current picks up the oil and churns it into a froth. The froth now fills the lower end of the motor causing the crank to now have to pass through it robbing horse power. The oil becomes aerated during all this churning. the aerated oil is now pumped through the motor causing a lack of lubrication to the bearings