I think modifing rules to meet current standards is fine, (i.e. front fairings being allowed past the front axle because street bikes come that way) but wholesale changes would affect the integrity of current records. Things that don't affect performance such as the tire behind the rear bodywork should be eliminated.
For those so inclined, an unlimited open-wheel bike should be allowed to run for time only. Wild as you want, but at your own risk. After all it's just the number we are all looking for. Hey Bill, fire up the welder, it's "Run what you Brung"