I can't recommend much on the suspension, I have to ask the guys on here myself. But for the engine, I have put a JE 80mm big bore kit in mine, I am still running the stock cam, fmf exhaust, and a 400ex carb. It runs very well. You won't have trouble keeping up on the trail with anyone. I downloaded the factory honda manual for five bucks. It should be all you need. Keep in mind that all of the 300ex transmissions up until '06 are the same as the 250x. You can buy them cheap on ebay. I bought one from a '05 model to go in my stroker that I am working on. 300ex crank will not work. The jug and head are the same. I saw a "buy it now" on ebay today for the 80mm big bore kit for $259 and free shipping. That is a deal. It comes with the jug, namura piston and gaskets. Just make sure all of your bearings are good, rod within spec. etc. Fmf, hmf, white brothers, supertrapp would all be a good choice. stay away from DG and cobra. they are for sound only. I am currently running a 13 tooth front sprocket, 36 tooth rear, with 20 inch rear tires. Works good for me in the woods. Keeps good torque and still allows you to wind it out on the open road. If you run the big bore kit you will have to go up several sizes on the main jet, Powroll has a good set of instructions for jetting your carb. on their site. I am going to use the Powroll stuff for my stroker, but I have no experience with it yet.