The Twoer (and the other lunchboxes) may be the most modded rig in the history of ham radio. Heathkit wanted it to be an economy radio so it was sold with absolutely no frills. Many of the mods were described over the years in articles in 73 magazine, which is now online in the public domain for non-commercial use. I made a pdf of numerous Twoer mods from 73 and put it online at
http://qsl.net/nz5n/TwoerGonsetRestoration.htm.
The articles in the pdf (numbers refer to the handwritten numbers on the lower left side of each page) are:
1 - Testing the Twoer
4 - More Selectivity for the Twoer
5 - VFOing the Twoer
6 - Push to Talk for the Sixer
9 - VFO Operation for the Twoer
11 - Squelch for the Twoer and Sixer
14 - Getting the Most From Your Twoer [xtal socket, meter, improved audio]
17 - Sixer to the Nth [power supply, vernier dial, antenna coupler, headphone jack, xtal socket]
19 - Twoer Talk [tank circuit mod for increased output, audio clipping, meter, neutralization]
21 - Operating Suggestions for the Twoer [xtal socket, antenna]
23 - Push to Talk (The Twoer Way)
24 - Twoer Modifications [VFO, AC/DC switch]
26 - The Twixer [mod to convert Twoer into 6 and 2 meter duo bander]
73, Bill NZ5N