When I was researching for my current guitar project I was intent on putting a FR on it. I have only seen one FR bridge on ebay that was specially made to be mounted without routing to an LP. It was $500 for the bridge only and it wasn't even new. FRs are really complicated. I wouldn't mess up a LP to mount one if you don't know what you're doing. If you are intent on a trem for the LP, get a Bigsby and get a really good roller bridge or special saddles for the existing bridge and install a self lubing nut and locking tuners. If you're careful and set it up perfectly, you should be able to use the trem pretty hard.