Here is a how to on constructing a funeral carriage. This is not a detailed project just a few pictures and pointers on how I constructed mine. This is not a weekend project nor a beginner project. Mine took me 3 months of assembly and thought process to accomplish. First I would reccomend doing a search on funeral carriage pictures, try to pick a style get a feel for size. I modeled mine after a Merts and Riddle coach. Similar to the carriage at Walt Disney World.
I dont have a formal list of materials for this project
Here I am in front of WDW's funeral carriage its about 6-6'-6" tall 8' coffin area in length. About 4'-0"-4'-6" wide. The coachmans seat will add about 3'0" to the overall length. 
Here is the finished project with my wife posing with me in our costumes
You can see the basic framework assembled. I used two 2x4x12's for the main frame. 2x4's were used for the cross members. The front and rear uprights will make up the coffin area.
Here you can see the carriage from the rear. On each side of the main frame I attached struts to support the bow of the carriage. I used 1x4 stringers for the bow of the carriage. I made a trough on my drive and wrapped the lumber in towels, then poured bowling water on the lumber and let it soak for a while. Once it was ready I attached it slowly to each stringer and bowed the lumber. I used strong screws for this don't want one of those coming loose and popping me. Be sure to pick lumber without any blemishes or knots when the lumber dries they can be a potential weekspot and break.
Here is the carriage with the plywood attached. I used two pieces of 1/4" plexiglass for the side windows. It bends and can be held in place by wooden cleats.Once you get the glass in place you can put the top piece of plywood in place. You will notice the rear of my coach has a slight roof over the rear doors. Basically its your call on how you want it to look.
Here is a shot with the moulding in place
Now with a shiny coat of glossy black latex paint. 
Here is one of the carriage wheels I picked up at a local trade days location. Unfortunately this didnt work out. I eventually went to a more pratical design since the carriage was just supposed to roll from the garage to the yard once a year.
A shot of the carriage after paint from the rear.
Here are the doors to the rear compartment
Assembly of the coachmans seat.
Assembly of the coachmans seat.
I do not have any pictures of the fifth wheel construction. Mine was wooden with two sheets of 3/4" plywood. I channeled it and set marbles in place with graphite dust held with one 3/4" bolt in the center. It was attached between the front axle and the bottom of the coachman's seat. I suggest doing some research and constructing what will work for you. The wheels were two sheets of 3/4" plywood sandwiched and glued then screwd together. After it was set I cut out the wheels with my jigsaw and then using my router I rounded the spokes. I made the rear wheels 48" and the fromt 36" Due to the weight of my carriage the wheels had to be replaced twice in its 3 seasons in my front yard due to rain. The axle was a fence post held to 3 pieces of bent flat steel that acted as leaf springs. A closet rod was run through the post and using a lag bolt for the wheel to be attached to. Pre drill this or it will split the rod and your out of luck. Basically I built this just by rough sizing form pictures there are no formal drawings or plans to create this carriage. Take your time and make changes where you think are needed to achieve your results.
