You dont need it welded in for NHRA. It can be bolted but it needs to have 6" x 6" x 1/4" steel plates on eachmounting point base on top and bottom of the floorpan. It also requires 1/2" bolts. The issue is the car only has a few places that are safe to mount the rear braces. The plates would not be flat but would be bent to conform to the floor pan. So tobolt ina pre-made rollbar and make it NHRA legal would stillneed somebody that can mig/tig weld to assemble the pre-bent tubing. Then if you dont like the fit of where the main hoop or braces are you are stuck with it.
If youi have a custom rollbar done the install is fully welded to your subframe. Nobody I know will do a 6-point rollbarin chrome moly for 1000 so ForensicSteve got quite a deal.
My chrome moly six-point cost me $2300.

 

Maybe mine's not chrome molly? Steel would be cheaper right? If that's the case I must steel...cheaperbut heavier probably.

 

It could be mild steel. It is what most of the pr-fabbed rollbar kits are made with. The mild steel tubingrequires thicker walls so it is heavier. It is obviously not hurting your times!
That cage looks good painted now and running the front tubes in the A/C vent.

 

You can also check out Agent 47's pre-fab NHRA innerframe. Bolt or weld in options .

http://agentfortyseven.com/S197/NHRAinnerframe.html

~Matt