Didn't really plan for this to be my first post but such is life I suppose!
Ok I'm trying to identify a motor that was given to me that is a potential for a swap into my 46 1 1/2 (?) ton.
I already have a beautiful running 1976 1/2 ton van 250 (with integrated exhaust) mated to a th400 that I intended to swap into my 46. A previous owner swapped in a gmc 228 which is beyond seized so I'm figuring the 250 should fit.
Now the wrench...
I was given what I believe to be a different year 250 and would likely opt for the less smog equipped, more hp motor of the two if I can make that determination. The "mystery motor "has no smog equipment, (I'm in CA) I was told it was a 66. I don't believe that now and am looking for ideas what this motor came from and which is better for a daily driver truck.
Block: con2
377127 d127 right above dip stick
Intake casting:3859381
Exhaust casting 3881825
Looking at my note, I don't have the stamping by the distributor so I'll add that tomorrow. Oh! And this motor also has a broken (3 pieces) exhaust manifold so if I decide to run this one I need to source and purchase that.

Thanks!