Only bore to the next size if you need to, there is no power increase. As far as combos the options are endless and it all depends on how much you want to spend. If it were me on a tight budget..send your cylinders to get bored (if need be) and ported, send to a builder ON HERE that is an hq sponsor (fast, driveline, redline, Mac daddy, hjr, there are more) welded crank, added compression, timing and a nice set of trail pipes would give you a fun setup for the trails. Oil ratio you can run 40-1 with a good oil like klotz super tech or benol. Benol will separate in colder temps just an fyi.