Shure Beta 87 FET info needed please....

Hi got a wired beta 87 and wireless head both have broken FETs one was 2SK170 & other was 2Sk377 cant remember which was which as desperate measures I found some FETs inside some old tape cassette recorder condensor mics, one has 156 B9E on it ??????.....it works sounds good but Im wondering if its sounding its best ......can anyone advise me ??

are 2SK170 & 2SK377 the same ???
Anyone no anything about the 156 B9E from old cheap condensor ?
I cant find 2Sk170s at the mo how about BF245 2n3819 j305  ???

Thanks for reading..