Training & Nutrition - Weight vs Power - Increasing Muscle Mass

I know that increasing muscle output (watts) does not have a 1:1 correlation with increased muscle mass (hypertrophy) but at some point, gaining strength will require increasing muscle mass. What I want to know is what are the best training principles to follow to assure that increases in muscle output outpaces increases in mass to the greatest extent possible.

BTW, I have a background in powerlifting but several years ago developed weight related health problems and suffered neck, back, shoulder and knee injuries. I have since shifted my emphasis to weight control and cardio/respiratory development. I am seriously hooked on cycling and lean toward endurance/touring but like the challenges of hills and wind. I'm looking to become an overall stronger rider with gains in both strength and endurance. Any knowledgeble training advice would be greatly appreciated.

You're making it too complicated. Fast cyclists have BMIs between 22 and 25. The best climbers are around 22. TTers are around 23-24. Fat randonneurs like me are up around 25. The thing is that our internal stuff like heart and lungs are fairly similar, so personal perfection lies in getting the fat down to our personal healthy long-term lower limit, then adjusting our protein content to achieve a BMI consistent with our cycling goals. Lance had to lose 7 kilos of protein for his TdF comeback.

In the short term, the first few years of serious training are best focused on increasing power to weight by increasing power-endurance while not gaining weight. More aerobic power is the low hanging fruit in the beginning. Muscle mass doesn't have a heck of a lot to do with that, because those gains are mostly through increases in capilarization, heart stroke volume, and mitochondrial density.

What I want to know is what are the best training principles to follow to assure that increases in muscle output outpaces increases in mass to the greatest extent possible.
The principle of specificity. (and drop strength, strong, and stronger from your vocabulary)

If you have a background in powerlifting I'd forget about increasing muscle mass, if I were you, you have all you could possibly need. Where you will make gains is in your aerobic efficiency and therefore your ability to maintain a given output over an extended period of time.

Where you will make gains is in your aerobic efficiency and therefore your ability to maintain a given output over an extended period of time.
Improved efficiency does not lead to increased time to failure. (at least using the accepted meaning of efficiency). What you might mean is increased aerobic fitness will increase the ability to maintain an output over a longer duration.

I suspect you are already significantly stronger than just about any world class cyclist riding in the TDF. Strength is seldom a limiter to increasing your power on the bike. The peak pedal forces involved in riding at 400W (90RPM) are less than 100lbs.