Cool build plans.

On the face of it your tube substitutions all seem good. The 12SL7 and 6SL7 are the same except for the heater voltage (so nice when the ID numbers actually mean something and have relevance to what's inside the thing). From memory my Radiotron book refers searches on the 12AX7 to the 12SL7 page for operating specs so you should be right there. Have to have a look in the book on the EF184 to EF86 swap but I presume you have done your research.

I did have a cheeky 'a little heater for when in the dog house' comment floating in my head but I'll let out only the nice civil ones... Looking forward to see how your build turns out.... ;-) ...