For 135 and under no roll bar needed (but advised)
For 150 you will need a roll bar.. Yes you can bolt them in but must have 1/4" plates and at least 3/8" Grade 8 bolts nuts and washers. ( I prefer 7/16 grade 8's) Look at the examples in the ECTA rule book. You will need SFI approved seat belts to exceed 135 mph too.
I have an older build diary on my 1933 Vicky,,(2008) it shows the required 1/4 plates and all the bolt in location
Here is one pic,,, notice the 6 x 6 x .250 thick plates welded to the base of the cage,,, they bolt into 6 x 6 x .250 thick plates that are welded to the chassis.. using 4 bolts ( 7/16 grade 8's)
Hope this helps
Charles