Keep clear of the of the O-290 it has been out of production for some time now and parts are becoming a bit of a problem.
It was a narrow deck engine the crankcases are not as strong as the wide deck cases found on the later O-320/360 engines
For the power range that you are looking at the in my view the best engine for you would be the Lycoming O-320 with the low compression cylinders but it must be the later type with the wide deck crankcases or you will have the same problems as with the O-290.