so a farmer is giving me a datsun 510 and my dad used to race stock cars so i said why not throw one of his old racing motors in the smallest car i could ever emagine putting a v8 in. my only worry is if the frame will handle this much powwer... any advice on easy ways to beef up the frame so i dont twist every time i try to smoke someone off the start?  

Do Datsuns even have a conventional frame?  Without knowing too much, I would say a roll cage is one way to increase the rigidity, along with the safety.  

a cage would be your best bet with the car, and it shouldnt be too big a deal to get one thrown together for it. With the popularity of 510s on the track circuit there should be plenty available to stiffen up the chassis but with the V8 the cage would be the best.

Id personally go with a 302 for its compact dimensions over the 318, but if ya bleed Mopar, then the best of luck to ya with it. it sounds like itll be fun.  

I can't get too excited about a "V8-Dime" swap (a better use for an old-school Datsun [PL]510 would be to clone a BRE Trans-Am car(not a "Car Craft" project, but worthwhile nonetheless), or to sell it to some cash-spreading tuner who wants to go drifting).

However, the stock unibody ought to hold up to some modest bent-eight horsepower.  Plenty of 510s are home to various modern, high-horsepower turbocharged engines that test the strength of the unibody.

About 35 years ago, Popular Hot Rodding featured a build of a MoPar 340-powered Dodge Colt Wagon for the street (I think Bill Bagshaw built it).   The stock unibody apparently withstood an A-motor with ordinary bolt-ons.   There's no reason to believe that the 510 is any less substantial (unless it's a rust bucket). The big problems were fitting the exhaust and craming in enough radiator.

That being said, a V8 "Dime" would probably need to ditch the 510's stock IRS and the smallish front springs/struts/brakes are more than suspect.

A 302 would fit better than a 318 and there's a lot more speed equipment for the SBF than for a 318. At least one person claims to have swapped a Ford 302into a PL510.