The International Cessna^® 170 Association

My C-145 engine needs a total overhaul. Should I consider changing to an O-300 engine for since parts are so hard to obtain for the C-145? Is there an STC for this? What are things I need to consider?
Doug
'52 C-170B

You need to be more specific. George already mentioned that an O-300A and and C-145-2 are the same engine. In fact, they are both on the type certificate.
What parts are you referring to that are hard to obtain? Several shops that I am aware of are overhauling these engines regularly. The A,B, and C-145 use 8 bolt cranks that are not as plentiful. The only advantage to a C is that is uses a 6 bolt crank, which would require you to change your prop. The D model I believe is heavier due to the right angle starter adapter and the vacuum pump drive that no one needs, and again, would require a 6 bolt prop.
Unless you plan on having a prop strike why not overhaul your 145?