That's definitely a Mopar big block. It's hard to say from the pics which one it is. If it's a raised deck (RB) big block it will have a flat machined surface about 2" square right behind the water pump tot he drivers side, even with the intake mounting surface that will be stamped with the size and other information. The common RB series engines are the 413, 426(wedge and Hemi) and 440. If it's a B-series or low deck big block, the machined surface I mentioned for the RB series will not exist. Instead the information will be stamped just to the driver's side of the distributor, sort of behind it on a pad machined even with the passenger side head surface. Common B-series low deck big block engines are the 350, 361, 383 and 400.
If the water pump housing mounts directly to the front of the heads, it's most likely a RB series industrial engine. These things are easy to identify if you know what to look for but unfortunately none of the pics clearly show these identifying areas. The intake and carb is making me want to say it's a low deck B-series engine, but some of the industrial RB engines did come with small 2BBL carbs so it could still be a RB engine. The 413 and 440 industrial engines were in production through the '78 model year, the 361 and 400 versions were dropped much earlier.