I don't believe the forward faceing Car. would be that much us a problem as far as air flow goes.

Glows have forward faceing Carbs. and they do okay.
You may need to run a line from the back diaphram into a dead air space for reliable Carb. tuning.

Also if I remember right there is an issue with the Carb. being so close the the prop.

I don't know about a thrust washer, but Buck has been there and done that.
Homelite, Poulan, Echo, Ryobi and Stihl are the main ones and not to many of the Stihl, probally because of the cost.

Just go to a small engine shop and tell them what you are doing. They will probally give you a couple of projects.

I was amazed at how many good engines are in the scrap bin.