Id-ing a small block block!

[Hawssie]

I am just tearing into a 1969 C30 which I was told supposed to have a 350 in it.The truck model is CE31003. The engine casting number is 3959532 which is supposed to be a 1960 283 but was also used as a CE replacement block. The front deck space by the head does have a CE number: CE6N23635 and then 428XCA which I cant seem to find a "XCA" suffix code. It definitely looks like it was re-stamped. Sorry the picture isn't that good but you can see a part of a stamp below the '5" I think. I included the SPIC too. Any idea what this thing is? Im not very up on how to ID these in the first place but was trying via this site: http://www.crankshaftcoalition.com/w..._Chevy_engines