I did a trailer project along the lines of what you are talking about. I cosider myself a qualified trailer builder, only because I have built several, and modified several more. I work cheap, have a considerable junk pile and steel rack to pull supplies from, and it is still a lot of work, and time consuming. The other side as far as time, is I have a regular job, so working on trailers was the afternoon job, not my means of providing bread, so consider that also. The last fact, is I am cheap, so spending large amounts of money on a trailer to replace one that I have that will work just as well with a few modifications is usually not going to happen.
Trailer #1 was a 27' deckover, modified to haul a pair of Conversion Vans behind an angle deck one ton truck. It was a lot of work, took several weeks of every night work. Because I was working "for" somebody, modifying my trailer to fit their needs, it had to work, to their approval before they wrote the check. Problems were simple, trailer was too short, simple plan, extend it 10' with matching metal. Problem two, axle placement. The normal placement for a trailer pair of axles for a trailer this length was considered and followed. Then the truck didn't like it loaded with the vans and placement had to be moved. Problem three was decking material. I purchased a used trailer to strip the floor off, but the timing wasn't working out, so I purchased bar grading to deck the trailer out with. Good move on my part, bad move for the buyer, as now the trailer weighed 4700 pounds empty. He took delivery and I got a call two weeks later about a D.O.T problem with his vehicle. Seems the 7700 pound truck and 4700 pound trailer were eating into his 25999 or less license, so I took the bar grading off and installed the original aluminum flooring from the purchased trailer.(weight now at 3300) Bottom line for this was, doing it and getting it exactly right takes a lot of planning and expertise, so expect setbacks as far as getting it right unless you are easy to please or a trailer guru.
Trailer #2 was a 45' fifth wheel boat trailer that I shortened to a 20' deck, and made 12' of it into a dump trailer. I call it my ugly dump trailer, because it is, but it does work great, didn't cost me a lot of money ($100) but it took several weeks of work, a lot of spare materials and some great help from a friend.
If selling the existing trailer was an option and purchasing what I needed was within my spending limits, I definitely would consider doing that, even if I had to kick in a little extra because modifying a large trailer is a lot of work, and takes a lot of effort to get it exactly right or your going to have problems with it.
David from jax
