I have more of an engine background than chassis, but I know alot of people use the 68-74 Nova subframes. They are relatively common. You may also consider buying a kit offered by numerious chassis fabricators. Pick up a National Dragster or visit www.nhra.com to get phone numbers
Something to consider before hacking your frame up, Check the width of the Chevy subframe donor car. Most models are too wide for your truck application. This can cause lots of problems. They also don't look right. You might look into a Mustang II frontend crossmember kit. These are manufacuterd by numerous street rod companies and they have kits specifically designed for your truck. I have used these numerous times. FATMAN FABRICATIONS, HEIDTS, are a few good kit manufacturers. There are numerous good points to using the Mustang II kits and or components. The crossmember kit would be designed for your type of vehicle. This is a simple independant suspension with disc brakes and rack and pinion steering. Installation does not involve cutting up you frame and because the frame is not cut this means that the frontend sheetmetal mounts to the original mounting locations. The Must II suspensions ride nice and look right. Plus, if you can read and know how to weld (or know someone who welds), you can install these kits with no major problems. GOOD LUCK WITH YOUR PROJECT!
I have a '53 F100 that is subframed, the builder used a '77 Chevy Monte Carlo. The width was the same as the stock Ford. They joined it at the front of the cab and boxed the stock frame back to the back of the cab for strenth. If you have someone do it, or if you do it yourself MAKE SURE that everything is straight and measured up right. If not it will never drive right. Sure is nice having the power steering, coil springs, tilt column, power brakes...built like Henry should have done it! Good luck!