small block build ?
Well i would be open to suggestions i just want to do it right the first time. How will the stock rods holdup or do i need better?
Okay, well if you're serious on going to a 408 the 360 bottom end will be a lot easier to sell on as a complete balanced assembly.
Stock rods can be made to live at 500hp levels but really need upgraded bolts.
A complete stroker bottom end will give better value for money than picking out individual parts too.
Go with a kit using say, Scat cast crank, Scat I-beams and KB/Icon Forged dished pistons for safe use of pump gas.
Brian's first 410 build (featured in Car Craft) pretty much nailed this combo and made 485hp with RHS heads, a big hydraulic flat tappet cam and 750 carb.
IMO getting over 500hp is doable with the hydraulic cam and a slightly bigger carb, though a little extra head work might be needed.
Beyond that, a hydraulic roller or solid flat tappet would be needed to reach 550hp.