Why are you only going to use the front clip of the S-10? The best part about using the S-10 is that you can use the whole frame, it is an engineered frame and the front and rear suspension and brakes are all intended to work together as a package. This makes parts much easier to find, then when it comes time to bag it you can go buy an air bag suspension for an S-10. Since you probably want it low anyways, you can place the body as close to the frame as you want when you're doing it. I don't get why you would mess with an S-10 clip when you could do the entire frame swap.
I picked up my S-10 frame for $100 already stripped and had a $200 S-10 (with rust through the frame, the truck wasn't well taken care of) that I used for all the other donor pieces, like steering column, booster, booster brace, etc.
If you want to keep your '53 as a long box, an extended cab S-10 is the right wheelbase (124"). When I was looking for a frame I put an ad on an online classifieds site and they were coming out of the woodwork. I could have had about 5 extended cab frames for free or close to it.
