the main caps are cut down to be flush with block and an extension block for the oil pickup tube
how much the cutting weakens the main caps i cant say but i would replace them
you would need new caps (stock if you can find or billet$$) , hardware for main caps and oil pan, and remove the pickup extension and reinstall the pickup with correct hardware
you cant just bolt a in cap from another block and go ...they need to be fit.... and that means disassembling , a trip to machinist to fit them to the registers and line bore .