This is my giant 2nd post on this site. Anyway. I finally trailered my pickup to my house yesterday, which went fairly smoothly. I charged up the battery and fired it up to see what is the deal with the engine...(i never started the truck before purchase $600) The engine knocks very badly and I really dont want to replace the 305 engine thats in it with a 305. Ive opted to go with a 350 engine. My question is. There are 1pc rear main seal engines and 2pc. (the truck currently has a 1pc configuration) Now what are the complications of switching to the older style block?