Custom's are more economical? You mean because you're only paying for the options that you choose?
Whether you get free options in packages you want, or yes just get what you want. Many options can be done better and as cheap by 3rd party vendors for what you want. Ford is not a custom van builder: they make good trucks.
Things like the towing/transmission package and the paint you want are many times over cheaper than 3rd party vendors. Sometimes Ford options are not made for everyone, and cost a lot to build around them (i.e. - center consoles.)
Every van I've seen on a dealer lot so far is white and has a 3.7 l (except for extended vans w/ 3.5 l.) I will carefully go through the options and see if CrewVanMan can find one at a deep discount first. Then I will price one out as I want, and go from there. However, there is zero chance of getting a 3.5 l in anything except a goodyear blimp extended body style. Colors and towing packages are another thing in options I want to get right off. I may be wrong, but usually towing packages and TALL body styles don't come together with commercial vans or stock oem packages (they don't care if employees stoop, unless it is high repetition like UPS.)
A cargo van standard w/ just one slide door would work, but I can be flexible depending on windows and doors. I'm not real smart, but I have enough education to realize who is smart; and Ortin's build would be my infrastructure workings with only cosmetic or structures changed. There are lots of smart people here, but I just happen to like his spelled out train of thought from everything I've read so far (it's always easy to improve, but not when starting from scratch.) And if you change ANYTHING from OEM, you better do a lot of research first on how it effects all other systems involved (it's very complex and time consuming beyond asking surveys on the web sites). He has done that with 2 different tall long vans so far.
Therefore, my approximate priorities are: tall, long, 3.5l, tow package on transmission, yellow, and whatever else Ortin has mapped out which does not conflict with a motorcycle garage in the right rear. I try to look at all the posts I can, but Ortin is very systemic and custom vans are very complex in supporting systems, material handling, and man/machine ergonomic interfaces.
So the only thing I want from Ford is the engineered mechanical drive train options and paint options for economy. I'm not concerned with many options that just inflate the cost, and think I can find something as near cheap but a lot better in technology and closer to what I want (anything electronics or interior structure wise.) imo.