[Jeff Lee]

Wheelbase for 1968 - 1969 - 1970 AMX's are all the same, 97". You may be confused in that the overall length changed a few inches as a result of body overhang. But the wheelbase remains the same on all 2-seat AMX's.

I assume AMC sent out the 1970 sheetmetal, tail lights, dash, seats, etc. (even a 1970 VIN plate!) to the owners of the original 1969 SS/AMX's more because they wanted a new for 1970 product in front of the public.

The 1970 production heads are an improvement over 1969 and earlier production heads but in a SS application back then, I believe the 1969 ported Crane heads were better than a 1970 production head (remember, this was back when SS did not allow porting). Note: AMC did not send out new "dog leg" 1970 cylinder heads to the racers, only body change items.
The SS/AMX's were fast right off and continued to be so well into the 1970's. Several years ago the dog-leg cylinder head was approved as a superseded part; long after the cylinder head porting rules took affect.

The fact is, AMC was the poorest of the auto manufacturers. They could not justify building another 50+ cars (at a loss) in 1970. So they thought they could get around the NHRA mandate that all cars be "assembly line produced" by replacing the relevant parts with full corporate approval. Again, note AMC provided NEW 1970 AMX VIN plates! Clearly, this was the intent of the manufacturer that 1970 AMX SS cars were to be recognized and raced along with 1969 SS/AMX's. But rules are rules and once NHRA saw what was going on (and it wasn't a super-secrete deal either), they put a stop to it and advised all racers that if they wished to race an x-ram AMX then it would be a 1969 model. Numerous owners who made the conversions with AMC's blessings along with new paint jobs, parked the cars in disgust (gee, does anything ever change?). A friend of mine has one of those cars. It was raced in 1969, converted per factory recommendation and subsequently parked. The only good thing is the 1970 VIN plate allowed easy MVD allowance for this once "race only SS package car". The car accumulated 70,000 in street miles before my friend bought it and restored it; back to race day 1970 with 1970 parts still intact. It is #3 of 52 produced.

Now, however, an interesting argument could be made to re-instate the 1970 AMX as a x-ram car due to the new "crate motor" cars in S/SS.
This was, and no doubt about it, AMC's intentions.