I helped my son build a 340 duster with a 6 pack carb set up. We did the whole car, and he never wrecked it or even got a ticket, he came to races and we raced together. Did a 67 coronet with my daughter as well, probably the best money I ever spent in raising my kids. So keep your boys interested in something besides a cell phone. I currently am building a 440 for my street rod out of spare parts I have accumulated over the years, so its a budget like yours. Stock crank and rods with arp bolts, same 509 cam, used sealed power forged flat top pistons, they are forged with coatings on the shirts. They use a different alloy so they clearance like a cast piston. http://www.ebay.com/itm/New-Sealed-Power-Speed-Pro-L2266F-Forged-Piston-Set-8-440-Mopar-Flat-Top-1-991-/302433751535?epid=220083592&hash=item466a74d1ef:g:p-AAAOSw7cxZpxyq&vxp=mtr

Used closed chamber 915 heads with hardened seats on the exhaust, and used 440 intake valves. I have a seat and guide machine and its really hard not to crack a couple guide tops when pushing in new guides. I like to put liners in them instead, if they are not worn too much. I have never had the cracks cause any trouble.