If you are using a standard 1969 Nova V-8 front end, it was from a 3200 lbs vehicle rated for about 1700 lbs on the front.

The 1949 1/2 ton panel was about 3550 unloaded vehicle weight and was rated for about 1800 lbs on the front. 4500 was the approximate loaded weight, with maybe 90% of the load on the rear springs.

The original rear springs were most likely over-rated for the maximum rear end load of about 900 lbs.

With those specs, someone may be able to provide a safe and helpful answer.