HI Dalton,
It all depends on how your 6`4" is constituted. If you have long legs and a short body you are fine, if it is the other way around you need to check more detailed.
I´m 6`2" tall and fit in my RCR without any modfication. To be more detailed:
The legroom is plenty. I ´ve build a adjustable pedalbox ( see my build log) . With my length i don´t need to go in most forward position of the adjustability. RCR has an option to move the steering column out of your way if you have submarine sized feet.
I opted to go with a gurney bubble to give more space for driving the car with helmet on. This said with the legroom available you can adjust you seting position and head clearance by the inclination of your seat back rest ( move the seat forward and have more inclination and therefore more headspace).
If you don´t like a to much tilted back rest, RCR has the option for a 1" dropped floor.
I´ve been sitting in almost every make (CAV,SUPERFORMANCE,TORNADO,GTD;MDA and original cars).
SUPERFORMANCE comfortable to get in and out of seats because they have almost no side support on the seat cushion. THerefore you need to rely on your seatbelts to fix you in a performance application.
CAV: good seat position, good head space
TORNADO/GTD/CAV: all of them have a smaller leg compartment compared to the RCR: has the biggest leg space i know of ( dont know DRB). RCR seats have great side support (performance oriented) a great center seat position (Steering to seat to pedal on the RHD version). and a good head space.
MY OPINION, IT WILL FIT
My reco is to give craig a call and try to get a seat in a RCR close by.
If you look out for a used RCR check the for sale part of the FORUM, Ron´s car is awsome.
TOM