Hi there can any one tell me what the compression would go to on a boss 260 engine if I got the heads shaved as I want to put some cams in it but make it worth it also what gains would it get from port and polish job also what cams are the best for these motors

Depends on how much you shave them?
I'm not sure how much you can actually get away with either?
Unlike a pushrod engine you have a front cover which will also require a skim off the top edge to accomodate this and may cause an undesirable mismatch between intake and heads.
I'm sorry to say it but maybe it's a better option to build a better bottom end to gain both compression and strength required? The stock stuff ain't the greatest.
Stock chamber volume is about 52cc so you can calculate what you need to remove from that.