I hope you mean that the dbx box preserved the dynamics of those recordings you were capturing. Me, I wouldn't want the original dynamics altered in any way when taping (it audibly "pumps" if you push dynamic restoration more than 5-8%).
I have an Akai open reel that's 7.5 ips only, but I've done some experiments with my 3bx and some old green-box EMI tape. The resulting recordings are slightly airless, but there's still more air there than digital! I must have 20 ways to play a cd or digital file, all with different results, none do "air" well.
As for recording your vinyl today, surely your phono preamp before the BHK has a fixed line-out. You could use a splitter cable at that point, send the signal to the BHK Pre AND the tape deck or dbx box at the same time. Then monitor your recordings thru the BHK in your chosen tape input.