First thing on a deal like this is to verify what the guy selling it says is actually what it is. Verify the casting numbers to make sure it is in fact a 472/500 and not a 425 or 368. The valve covers do not look right for a mid 70s 472. The sellers comments about being a big block and that it was too big to fit in an 83 Monte kind of tells me the seller doesn’t know what he’s talking about (should be more along the lines of “I got in over my head”).
Comments like “ran when pulled from truck” always make me a little cautious (especially when Cadillac engines were not installed in trucks)...... how did it run and how long has it been sitting out in the elements.
I notice it is missing most of the accessories/brackets which can be a PIA to find and depending on the oil pan you may need to dig up a El Dorado pan or aftermarket one ($$$$). At a minimum you will want to pull the timing cover and replace the timing chain and put in new valve seals.
Depending on the year and compression a mid 70s 472 should make close to 500 foot pounds of torque around 2500 RPM and stock valve springs float at around 4200 RPM. Geared properly (highway gears in the 2.75-3.25 range) work very wells with these engines. Properly set up in say a G Body it's not too hard to get a fairly stock 472/500 into the 12-11s and still be very streetable.
If the engine needs rebuilt you’re looking at around $2000 for a stock rebuild.......start adding speed parts and it gets real expensive real quick.
What are you looking at putting it in? The Caddy engines are long and tall, and while they can be put in a lot of different vehicles it usually is not a “bolt in” deal and will require some amount of skill. The often listed 50 pound difference between the weights of a Small Block Chevy (like the 305/350s) and the 472/500 Caddy is in fact closer to 100-125 pounds. Things like springs and cooling system capabilities will need to be considered.
If you are planning such a swap be honest with yourself about your abilities to actually make it happen.