Actually I did a quick analysis of the isolated tracks for "Whole Lotta Love" and I would suggest Pre-Rola SM57 IR's for achieving that sound. The PR55 SM57 A1, B1 and C1 had many similarities to Jimmy Page's tone. If the PR55 EQ balance feels off try the PR75 SM57 C1. I also tried the HW cab and I think you're on the right track. I tried blending the same speaker SM57 option (D1) with the IR you had been using and I think it got even closer.
Give it a shot and let me know if my suggestions worked for you.
Tone wise I think the PR55 would probably be closest since Jimmy's tone is almost completely clean yet it has lots of low end roar to it.