Are the springs the same length as a sedan B/E? I guess they are.

XHD springs run about 142 lb/in and XHD + 1 full leaf runs around 172 lb/in. I run the XHD + 1 leaf on my E with 1.00 front bars. I added the leaf to get more rate... and it also compensated for the sag after a while on my MP XHD's.

With your bigger front bars and decent shocks I would suggest something in the 170 lb/in range as a start. Maybe start with XHD's and have your local spring shop add a leaf as/if necessary.