Tonawanda small block?

[bergy]

The "conv" designations were permanently part of the patterns when they were made. They reflected the planned casting conveyor when the pattern was made (could have been years earlier). They were not "tags" like the date codes & didn't represent which line the mold was actually made on. Remember the rule of thumb - iron patterns (which these were) typically lasted 100,000 molds before refurbishing. Aluminum patterns lasted 10,000 molds. Your block was cast off of pattern #11 in that family of patterns - which could have been in production for a long time.

the casting lines were

Line 1 - M4 Blocks

Line 2 - small blocks

Line 3 - M4 heads and all intakes

Line 4 - small block heads

Line 5 - water pumps, oil pumps, bearing caps, & misc. lower volume parts

Line 6 - same as line 5

Line 7 - was removed in early '60s

Line 8 - all brake drums