David-
I just purchased a 150/150, and i can tell you, it was WAY cheaper than doing the conversion myself. Depending on how cheaply you can acquire a 0-320. The STC from Del Air is $8000. Then you have to buy the engine, so maybe 8-13k, depending on if you want a new-used-low time-midtime, whatever. Then, if you aren't an A&P, you have to pay someone 65-70 bucks an hour to install it. Quite an undertaking, unless you are absolutely IN LOVE with your airframe. Look at the club newsletter from early 03, the article is titled "everything you ever wanted to know about the 150 conversion" or something like that. You may have to wait awhile for a good one to become available near you, but hey, you have 300 hrs! I got a 77 150M with a mid time 0-320 for less than 25k. Look in the mountain states.