Is it ok just to bolt the seatbelts to the floor pan whereever you feel is comfortable? Does there have to be any welds? How about the part where you mount it to your roll cage behind the seat, is there any certian way you have to do this to pass tech? Any help would be appreciated
It depends on the class you intend to race in. NHRA rule 10:11 says:
"All cars not required by Class Requirements to use SFI 16.1 driver restraint systems must be equipped with an accepted quick-release-type driver seat belt."
Since you are installing a 5-point harness you will be required to follow the rules pertaining to that system. Rule 10:5 says:
"All seat-belt and shoulder harness hardware must be originally designed to be used with each other and produced by the same manufacturer. ... Cars using OEM or OEM-type seat may route crotch strap in front of seat instead of through seat. ... All harness sections must be mounted to the frame, crossmember, or reinforced mounting, and installed to limit driver's body travel both upward and forward. Seat belts may not be wrapped around lower framerails."
The accompanying diagram indicates that the seat belt is anchored at a 45 degree angle to the floor of the car and the shoulder harness is mounted level with the shoulders to 4" below the shoulders.
Your best bet is to invest in the NHRA rulebook if you plan on racing.
Get a tech manual. The seatbelts should also come with a installation guide.
I would suggest mounting the belts to the floorpan at a reinforced point, such as the seat mounting bolts. If that's a no go, then use some large fender washers on each side of the floor so as to create a larger "tear through" area.