Unfortunately clubhead speed has very little to do with strength and club head speed has a minimal effect on distance.
Look at Charles Howel III - he is a great example. He is not particularly strong nor is he particularly large. He's around 6ft and 155lbs... What about Hank Kuehne, he's 6ft2" and weighs 205lbs - not big and nor his he anywhere near as strong physically as Vijay, Tiger, Phil or Ernie ... How many times have you seen HUGE guys tee off and hardly make the 250yd mark?
Let's do the relationship between swingspeed and distance first, that's the easiest part. For every 1mph in added swing speed, expect no more than 2 yards in distance. That's a scientific fact ... proven time and time again and it's the ratio they use at
Callaway,
Titleist, etc. It is also near impossible for a good player to increase their clubhead speed by more than 10%-15% without specialist coaching and physical development - that's a fact. So, you'll never go from a short hitter to a long one or from an average hitter to a bomber!
You're gonna say "but .... but ..." I know. Jason Zuback etc. gained huge distances by being strong and swinging fast. The truth is they swing at around 180mph - that alone is 360yards! Hello ...
Distance comes from a combination of: ballistic launch, spin rate and speed. To max your distance, you need to find your optimum of each component and then build a club that gives you the result.
My advice ... don't do weights and fitness expecting large changes in distance becuase it isn't going to happen. Where you will find a difference is being able to swing more consistantly, you'll have increased aerobic fitness and your muscles will be able to absorb and retain more oxygen which will increase performance and stamina. Sure, there will an increased strength factor but that's not where power comes from ...
Power comes from the core - the core being your hips, stomach muscles and added flexibility to increae the 'X' factor of your swing. Now the 'X' factor is the difference in angle between you hip turn and shoulder turn. The larger that angle is, the more able you are to generate swing power. Look at Jason Zuback as an example, Big JD is another but one of the best examples you'll see is Hank Keuhne, his distance comes from power and not strength. John Dayly comes from that 360* swing and pure clubhead speed and not strength either.
Distance is technique ...