skip the probe piston and just buy this kit:
i ran a similar rotating assembly up to 6500rpm and made over 500hp with it and never had any issues.
i would strongly suggest going with a hyd roller instead of the flat tappet cam. if you bought it from summit then i would bet that they would take the cam back and credit you toward the hyd roller cam. besides budget, there is pretty much no reason to go with a flat tappet cam anymore. you spend about $300.00 more for the roller valve train but yet you get considerable more power and longevity.
i personally would also ditch the 650 double pumper, it doesn't sound as if you will be using this more as a race car, so there is no real point in the mechanical secondaries. i would suggest getting a holley 3310 750 vac secondary carb.