Commercially available 6M amplifiers tend to be hard to come by, so many amateurs build their own out of necessity.
Converting a Heathkit SB-220 Amplifier to 6 Meters by Mikhail Chirkov UN8GC, Steve Gilbert K1SG, and John McManus W1JJ April 2008 QST pp. 38-40. Here are the details on converting the highly popular Heathkit SB-220 to work on the magic band, 6M!
A Compact "Brick" for 6 Meters
QST October 1990, pp. 18-21
Build a 6-meter 100 watt amplifier using a MRF140 FET.
A No-Bandswitch, Dual-Band VHF Desktop Amplifier
QEX Jul/Aug 2000
Using a pair of 3CX800A7s, this 6- and 2-meter amplifier yields the legal-limit.
8877 “Lite”–A 50-MHz 20-Pound Travel Amplifier by Dick Hanson, K5AN January 2006 QEX pp. 41-46. This portable amplifier will put out 1500 watts with 50 watts input.
An Experimental Solid-State Kilowatt Linear Amplifier for 2 to 54 MHz
QST September 1992, pp. 19-23
This is not a step-by-step construction article, but a springboard from which to build a 35-pound kilowatt solid-state amplifier.
A Compact 1-kW 2-50 MHz Solid-State Amplifier
QEX July 1990, pp. 3-8