It can be done but you will have a real-time of it. Better off buying the cheapest kit. I'm also frugal bastard. The ring that holds the pump secure though... my thoughts were to wrap the pump with a fuel-proof material to increase the diameter enough that it wouldn't move around horizontally. Or use an epoxy/resin that won't break down to fill the diameter gap. You use clay and mold release spray to pour something and the pump would not be stuck in the mold. The only thing I found was Loctite E-120HP fully resistant to E85 but not cheap.
Once it's inserted into the basket it doesn't have up and down room. The spacers are very basic can be had easy.
Anyways you are free to use my drawings. These are estimates. I take no responsibility for your decisions.
I plan on a full dirtbag write-up for DIY MPI eventually. Still need some work on the fuel controllers. Look at the install guides and McMaster-Carr, you could pull it off