I removed the thick bottom overload leaf from the stock D-100 long bed springs.
I just put them back under the 440 truck. tthis is how it sits.
to me it looks about like what you got -/+ 1 inch in the pic you have in the driveway.
even though I have it tubbed with a wider wheel/tire combo it sits just a tad lower than the 85 stepside which i UN-flip floped back to stock with a 235/75/15 tire.
are you against tubbing the bed for more wheel/tire?
IMHO,I think the only thing holding up more rim backset is the stock wheel tub.
join the group and chop your 8 3/4 to A-body specs and stuff some 12s with fattys under it.