LS6 454

I need some help.
I am currently looking at a car to buy. it is claimed to have a 1970 LS6 454 under the hood. What are the easiest wats to make sure it is a real 1970 LS6. thanks for your help  

factory 454 torsion dampers, have a counterweight running halfway around the inside diameter.  396/402, availible in 1970, won't have it.

According to the Guide to Muscle Cars magazine, the LS6 in 1970 had rectangle port, closed chamber heads, an L-72 type solid lifter cam, and a Holley 800cfm on a high riser aluminum intake (Corvette, maybe part #3933163) or low riser (Chevelle, tho the cowl induction may have had a high riser). In '71, open chamber aluminum heads lowered the HP to 425 and only went into Corvettes.

Car Craft Jan 89 lists a 450hp, TH400 LS6 having a CRR code, and with the muncie, crv.  the ls5 was crq w/ the th400, crt w/ muncie.

BUT, there was many crate LS-6's sold, under part number 3981820 for the shortblock, 366250 for the longblock. Guess how many probably ended up in SS clones?  The tolerances are as bad as those on 1966 426Hemis, for the same reason--the builders expected the customer would rebuild, so why waste money on making parts fit well enough to warantee?  

factory 454 torsion dampers, have a counterweight running halfway around the inside diameter.  396/402, availible in 1970, won't have it.

According to the Guide to Muscle Cars magazine, the LS6 in 1970 had rectangle port, closed chamber heads, an L-72 type solid lifter cam, and a Holley 800cfm on a high riser aluminum intake (Corvette) or low riser (Chevelle, tho the cowl induction may have had a high riser). In '71, open chamber aluminum heads lowered the HP to 425 and only went into Corvettes.

Car Craft Jan 89 lists a 450hp, TH400 LS6 having a CRR code, and with the muncie, crv.  the ls5 was crq w/ the th400, crt w/ muncie.

BUT, there was many crate LS-6's sold, under part number 3981820 for the shortblock, 366250 for the longblock. Guess how many probably ended up in SS clones?