The J header weighs about 30 pounds.
There are support brackets that come
off of the engine block
at the oil pan to help support the header.
If yours are missing, they are available on ebay.
Exhaust headers from Bud Faubel's Daytona G
They are different than J/ramK. The left side collector tubes are very similar but the main tube is notably wider diameter and a little shorter so that it doesn’t appear that it would snake down past the torsion bar (F/G also longer wheel base than J/ram K of course). The right side has more apparent differences in the casting from J/ram K with the combined tubes for #2,#4,#6 exhaust ports.
Left side exhaust header 300G Daytona
Right side exhaust header 300G Daytona