Club Cobra - SBC Damper

OK..... This is not a big deal at all. Chebbie stuff is all interchangeable if you match the correct timing cover or tab location that is on the cover.
In short there are only 2 versions or timing mark locations on the harmonic balancer itself. The difference between the 2 versions is 9 degrees. The diameter is variable but the fact they are all balanced to ZERO offset is the key. There is a small block H.B. that is offset weighted but that is for the 400 cubic inch motor that is not internally balanced.
The width changes between applications so this could throw off pulley alignment but bolt hole spacing for pulleys is all the same so no big deal.
You need to match width so pulleys line up is correct but the diameter is not a functional concern. The thing that is giving you grief is the timing cover or its tab location. All the earlier models had a bolt on timing mark tab. This is located on the 2 bolts just above the left side of the block pan rail and straddles a dowel pin. (if looking at block from front of car it is on THE RIGHT SIDE at about 3 O'Clock) on the left if in drivers seat.
Later timing covers and HB. used a timing tab spot welded to the cover and not bolted in place. This tab is welded to cover at about 2 O clock as viewed from the front of car looking in at the HB (Harmonic Bal).
Bring number 1 piston up to top dead center and find out where the HB mark is at. Simply place aftermarket timing cover (TAB) to match the location of mark on HB when on TDC. Most accurate method for TDC is to put something like a plastic wire tie in plug hole and find top of piston travel. You could watch #6 valve rock of int & ex where the are 1/2 up and 1/2 down but this can be off with cam being advanced or retarded a bit. No big deal...... it will be easy to fix. Jeff C