4T is known and a '68 Chevelle L35 396/325 manual. . 4U is also known and a '68 Chevelle L34 396/350 manual. .
I'll look tonite as I have an old Canadian book w/ some numeric codes I've never found elsewhere....just in case it's there?
I fixed a '63 Vette about 20 years ago that had a small block w/ 77 as the suffix....sure enough it was in the old book as a '67 Chevelle 283 so you never know?
~ Pete