Mick - I'll try to provide a bit more info to satisfy curiosity, but as you seem to indicate, the info on Mexican blocks is pretty limited. I did some web searching and found a few articles, like 1955 1 Series posted above, including ones in the HAMB and a couple other forums. This old sales ad in the HAMB
292 Goodwrench Replacement Engine provided good info, as well as this thread on
Strange Adjusters on 292 head.
From that information I took the noted part number GM# 10121028 and searched
GMPartswiki. That lead to the screen shot below, which shows the engine GM# 10121028 was for 1985-86 Goodwrench 292 replacement/remanufactured export engines (it doesn''t say Made In Mexico in the listing, but I think you can suppose that to be the case).
In looking closer at your pictures and the others found, I think the "GM 4.8 6" cast in the block just indicates its a GM 4.8 liter (292 ci) 6 cylinder. Maybe a SWAG on my part, but I think the "93" denotes the 93rd day of the year built and the "86" indicates the year of manufacture "1986".
IIRC, somewhere in one of the HAMB threads there was a comment that this 292 was considered superior to US blocks because it was a thicker casting.
Enough to satisfy your curiosity???
