Thanks, GGG. That's a good idea by MTH. Several times in the past I could have used it.
I'll add for the benefit of others, that on the kit I'm using now, the bottom leg of the aluminum heat sink has to be S-bent to clear the front of the board.
Also, the manual, page 13, says to mount the heat sink to the rectifier using screw "P" which is defined on page 3 as being 6/32 by 8mm. The heat sink in my kit would not accommodate a 6/32 screw, but a 4-40 machine screw fit nicely, easily cutting a thread in the back flange. There is no relay behind the rectifier that can be hit, so I didn't have to cut the 4-40 shorter.