Alan,
If I'm reading you correctly, you're going to keep the current trailer and make some upgrades and modifactions, right? If so, contact Rocket directly and see if they can give you the specs to set it up. Here is their web site -
http://www.boatsho.com/FL/fb5402/ind...ealerID=fb5402 .
If you're going to buy a new trailer, typically the manufacturer can set it up for you just by knowing the make and size of your boat.