Having installed a G-body front suspension on my 54 Chevy truck (same as your 49) I will share the following first hand knowledge:
2nd Generation Camaro/Firebird (70-81) is too wide for the AD series trucks unless you want to leave the ride height high. If installed in a lowered configuration you WILL have tire to fender clearance issues or tire to frame clearance issues if you try to run a tire wider that 7 inches and bigger than 15 inches.
G-body subframe works well but is fabrication intensive. Clearance issues between the steering box and core support will result in modified radiator mounting. Mine works great with IROC Camaro front springs but I would not do it again.
1st Generation Camaro/Firebird (67-69) is a rear steer configuration which works well and has the correct track width but these are hard to find.
One thing to keep in mind about any subframe modification is you will need to spend the time to replace every component and bushing to ensure it works well when you are done. If you can fabricate and weld then the installation of a subframe suspension should be considered. If you intend to farm that out I would consider another option.
My suggestion is to use one of the IFS kits out there for these truck. They install easily, have rack and pinion steering, and good brakes. The small additional cost that may be incurred is more than made up for with good sheet metal alignment, better resale value, better performance and peace of mind.
The S10 chassis swap is not the solution many others think it is. In my opinion you are paying the same amount of money for one of the aftermarket kits that a decent IFS kit would cost and the truck will still sit too high for my tastes without swapping out the spindles to lower the front. You also have the related headaches of properly setting the engine & trans, fuel tank, running boards, etc.