Trailer Question - spec and set up needed

[abl1111]

What's up guys. Long time, no type. Thinking about pulling her out ( a 1975 23' Tsunami ) within the next month, and I need some trailer specs from you. The trailer that came w/ my boat, a Florida-made brand, mid 80's, ROCKET trailer, is a P.O.S., but it will work perfectly for the (2) hauls a season I do. It probably was a great trailer when new - double axle, I-beam construction.

OK, if you could give me some measurements and advice:

What is the dead center distance of the bunk beds for your trailer ? Roughly, what is the height of these beds from the trailer frame?

Anyone know where I can read up on, or how to fit my boat to the trailer ( I know it is supposed to be the other way around, but this is what I have ) ? ---- i.e. Haul the boat on the trailer then using bottle jacks lift the boat and correctly adjust the bunks, rollers, tongue weight - etc, so it is "right"

Lastly, where is the cheapest place to buy 12" stoltz rollers w/ brackets ?

Thx,

Alan