ScotI.......some more info is required to compare rates.
Ridetech quotes 1020 but their arm length might be 6".....entirely possible.
We need to know that arm length in order to compare.
Using this calculator......
https://swayaway.com/tech-room/torsi...te-calculator/
you can compare a 6" arm length to 12" arm for the same bar. Simple multiplication.....the short bar is double the rate of the long for the same diameter and same pillow block spacing.
Also if you shorten your BAR LENGTH (and locating pillow blocks closer) to get inside your chassis rails , you're gonna raise the rate massive. Warning....if your bar length is short relative to the amount of BEND in the arms to get out to your 39.3" then the amount of deflection in the ARMS reduces the bar rate and eventually fracture an arm at the pillow block area. Shortening the straight section of bar increases prolly by the square of change.....shorten 1" = 100# change.....shorten 2" = 400# change.
A HOLLOW BAR is only slightly lower in rate compared to a solid bar ..... how much? I don't know but maybe 5 or 10%. Gotta be on Internet somewhere.
My suggestion in this whole subject would be to calculate the wheel rate of a STOCK truck compared to your MODIFIED wheel rate then use the same percentage of factory bar to your desired bar. Don't OVERPOWER your spring/shock combo.
(ignoring sway bar....so just use the dimensions from inner lower pickup point to spring /shock mount, and inner point to tire contact dimension multiplied into spring rate)