[Arran]

 This is one of the reasons why I haven't bothered doing anything with the Philco 90 chassis I have sitting in the basement as yet, unless I find a cabinet with speaker or a slightly rough 90 with same. When you see complete project 90s sell for under $300 but see people pay that much for a speaker with a rough cone, plus shipping, it doesn't make any sense to try piecing a set together from parts. Those were pretty lousy sounding speakers to begin with, the only reason to buy one is to make an authentic factory correct set, for much less then that one could pick up a period Utah, a Magnavox, or a Lansing speaker of the same size, and similar electrical specs, in decent shape. With a Philco 70 this is even more so, there are twice as many 70s as there are 90s out there, and three times as many 20s as there are 90s, all used similar pie pan speakers, except the ones from model 20s had that large nut holding the pole piece in place as Mike (Morzh) stated.
Regards
Arran