1971 Blazer - original engine?

[71swb4x4]

The 350 in my Blazer is stuck. I have thought about buying a running small block to throw in just to get the Blazer running. First I thought I should decode the engine to see exactly what I have. If it's a 307, I have no problem replacing it. But if it's the original motor I will think twice.

So here is what I found:
V0301TBG
The V tells me it was built in Flint. 0301 tell me it was built on March 1st. TBG tells me it was installed in a 1971 truck, 1/2 ton to 3/4 ton. So it's starting to look like the original motor.

The Blazer VIN tag on the door has a March 1971 build date on it. The first 7 digits are KE181S which decode as a 4x4 V8 1/2 ton Blazer built in 1971 in St Louis.

While I realize there are no numbers matching engines in this truck, this one certainly is as close as we can get. Since everything lines up I think I should try to save this 350 before I buy a replacement.

Does anyone see anything that I am missing here?