[auto10x]

I have heard / seen several reasons why one 351W block may be more desireable than another:
To qualify for emmission exemption (older is better)
Thicker webs ('74 and earlier)
Slightly lower / higher deck heights ('69 & '70 / '71 on up)
Are there other reasons? Other than for emission qualifications, are there really significant reasons to go with one rather than another? If so, which is the most desireable.
Thanks,
auto10x
Bill