I have had a 416 before and it was a very good and reliable engine. I bought the engine with the p&p done so I don't k now a price on that. The heavy duty studs I do recommend! I just used a comectic gasket kit. Make sure that it is not smaller that 87 mm. You should be good with premium pump gas--93 is what I am running now. I am not for sure on the 450r carb. I am just running a stock 400ex carb. You may wanna think about getting the flywheel lightened and advancing the timing. The lightened flywheel will let it rev quicker and the advanced timing give it more low end. Just my thoughts.
My drinking team has a racing problem!