I hate to be that guy but here I am. When I see people post engine numbers for ID I just figured they were too lazy to look them up themselves. They knew someone with the stovebolt gene would look it up for them. I'm going to have to rethink my views on that. I sincerely tried to find information on these numbers and the history of the Mexican block. Some say it's better and some say it's not. AI said it was a mystery. I can't wait for that to take over. I managed to decode that it was a Mexican block without AI because it says "Made in Mexico" on it. I do like the uniqueness of the casting on the drivers side. So if someone feels like helping that guy out I would appreciate it. Thank you for your time.
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???
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
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???
Thank you I think I'm good now. I'll put her in the 292 line up. Now I have 3 running, 2 complete and 2 blocks with heads. Does that qualify as an addiction? I drove 10 hours yesterday to buy a 292 abandoned project engine newly rebuilt with 194 valves and a custom ground cam complete for $500 with paperwork. I got the Mexican block another complete short block and 2 stock heads for another $250. He is a V-8 racer and has no use for them. He's going to dig a few more 250's and 292's out for me this winter. everything is indoors with concrete floors.
I have a Mexico 350 4 bolt main block, and it is pretty much the same story. There seems to be little information available. Some say they are good blocks and others say they are junk.
Thank you I think I'm good now. I'll put her in the 292 line up. Now I have 3 running, 2 complete and 2 blocks with heads. Does that qualify as an addiction?
Mick - You know the answer to that question is YES - LOL! Glad to offer a helping hand to feed your addiction (and mine as I enjoy digging up this kind of info). Enjoy your collecting!
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
Glad to offer a helping hand to feed your addiction (and mine as I enjoy digging up this kind of info). 
Enjoy your collecting! 