They will bore out the housing, fabricate and install stainless sleeves. Assume about 1/16" thick. The discussion was to bore out about half the available material. This is a precision operation, I don't think even an above average garage mechanic could pull it off. The alignment of the two bores must be very exact, even a very slight misalignment will cause the bearings to bind. A machinist has a special machine for it. It is similar to boring the cam bearings in an engine. I figured it would be cheaper because it is a pretty routine operation for an engine builder, but the "engine builder" shops I called didn't want to even look at it if it wasn't an engine. So I had to take it is a higher end machinist.
I don't think delrin is a good idea. I just looked it up, and Delrin AF (the formulation for bearings) is slightly harder than aluminum. Stainless is harder than both. The tensile strength of delrin is much much lower than either aluminum or stainless. My machinist recommended hardened steel because he was concerned stainless might be too soft.
Anecdotally, the sheaves that I used to route the lines to the wheel use delrin bearings, and they did not survive either. Still intact and working, but very loose and in need of replacement. Not sure of the grade of that delrin, probably cheap.
Yes, the 402 has 3 bearings total, and that would be even stronger. But if this lasts twice as long as original, that is 60k miles, and I probably won't be sailing any more than that. The 402 is also a larger diameter, so the engine controls will not fit, the compass will not fit (but an adapter is available) and the steering wheel will be moved back by about an inch. I have already had heavier crew complain the steering needs moved forward, so I'd rather not deal with all of that. If the 402 was dimensionally the same as the 335 and the other parts all fit, I would buy one new. But everything else makes it too much of a compromise for me.