Interesting. I am building a buggy with 3.9/904/eco/d300. This is with 2011 rear sterling that has a e locker which limits me to 4.88 unless I get an older housing....with 40's this gives me 94.92 in double low.
your current numbers in low are 66.9 , with 5.38s you drop to 73.75.
granted you...