If it's a '68 engine, it's a 375hp 428! Look on the side of the block and look for the #'s 428 between the freeze plugs. Also check the block part # on the driver's side behind the head. A 400 would be 9790071, 428 is 9792968. Specs for tune-up are as follows:

timing- 9 degrees for all V-8
dwell- 28-32
Steve