I run comp solid roller lifters with the larger wheel, don't think they are considered a "retrofit" lifter though. They also have the tie bar on the inside instead of the cylinder side.
On the wheel diameter/speed thing is to use a boat trailer tire to explain. A trailer with a 8" wheel and say a 15" tall tire will have a greater bearing speed than a 20" tall tire on a 13" wheel. In a mile they both travel the same distance but the smaller tire has to make more revolutions.
