I don't think you will find anyone that runs 500' ice, they are 660' (201m).
Thats more grass drag with 500'
I think Flannery old Polaris F/A ran a 6.04 in 500'
Jeff Lausten ran 86 mph in 500' on his 73 Yamaha SR
those look to be cat or poalris rack carbs and the spacing is just fine also vmax flatslide are a direct bolt on too .............
one of our bone stock 75 433 gpx's ran 6.40 on the grass in 500 feet
last year ......give us a rubber track as a luanch pad and it could be quicker .........regardless that sled still moves pretty good