Roger, a friend of mine builds rods for a living and he has built several First Series Chevy trucks. He will not do a frame clip. In a professional shop, like his, a clip costs a lot more than an after market Mustang II. By the time you rebuild your donor front end you will have almost as much in parts and clipping requires a lot more labor. And if you dont get a clip right you will go down the highway catty wampus.

Consider using your stock frame with a Chassis Engineering bolt in parallel spring rear end kit and their transmission crossmember and motor mounts. In front use a Mustang II crossmember from one of the reputable suppliers.

Another rod building friend, also named Roger, is building a First Series panel delivery (same chassis as the pick up) for a customer. He is using a RB's rolling chassis. It was in the $10K range delivered. But there was a lot of value in that package.

I agree, a chassis swap or a front end clip requires the same investment (time and money) and, when compared to a properly updated stock frame, results in less end value.