CR500 Quad VS Banshee... What to Expect or do?

[QuicktimeRacing]

I'm about midway through the completion of my CR500 (1985) in a 400ex frame project and am trying to get the rest of my ducks in a row. As of right now I have the motor mounted, a 250R swingarm in place which I have been told is lighter and longer then the stock 400 style, a 450R Radiator, and an FMF race pipe off a 250R which I may modify the inlet and outlet slightly to increase flow.
What I'm wondering here is whether or not I should go real crazy with the engine rebuild or not? My buddy has a Banshee that as I recall laid down 70+ on the dyno and he never quits running his mouth about how fast his bike is and yadda yadda yadda. Anyhow what I'm wondering here is how close should I expect the two bikes to be in a race? I don't know that I can go through all the grief of this swap just to hear how his "built" Banshee can smoke it. I've always heard theres no replacement for displacement but I just dont know if thats enough to get me in front. What do guys think? Should I do some porting and step up to a cool head for increased compression? If it's not neccesary I'd rather not spend the money on the head. Let me know what you guys think of the power potential and what to expect. Any info into the 500 power points or weak points are also appreciated. Thanks in advance... :)

[rooster300ex]

i'm no expert, but i would do the extra hop ups to yours so you will know you will smoke a shee with 70+hp. I think a stock 500r motor puts out like 60-65hp.

[GPracer2500]

CR500 is more like ~55hp (but also has ~45lb/ft of torque) to one wheel. I'm not sure about an 85' though. Probably not too different.

Gussetting the EX frame is probably wise. I've heard of CR500/EX hybrids rattling frames apart because of the vibration [shrug].

[Mechanix311]

i have built 2 500 quads using 85 model year 500 motors and i hate to burst your bubble but it will get beat. Their is just something about the motor that makes it not a good choice to put in a quad frame. My gearing always seemed to be off and I couldnt seem to hang on to the handlebars long enough to complete a drag race because my hands would go numb from all the vibration. Both of my quads are now sold for this reason. 85 put out the most horsepower though.