the C5A number is probably a vin, indicating 1965 or 75, the TJH says it's a 350 from a C10 to a 3500 .... the 88766954 is a casting code, might further ID the year and 2 bolt or 4 bolt main, other differences are less important, check for any date codes shown the first page of the Z28 site .... and all that's meaningless for trans ID, any trans will bolt to a 350

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir
"When we tug a single thing on an old truck, we find it falls off" ~ me
Some TF series details & TF heater pics