Switching focus from weight loss to muscle gain

Folks, I could use some input from those of you who have been around the block....especially those who have already achieved or are on the way to achieving the same goals as I am working towards. I'm 42, and back in high school and even one year into college I was an athlete (never a blue chipper, but good enough to get into a DIII school for football and wrestling). I have never been "defined", but did have mass back in the day and then through most of my 20's when I was working quite physical labor in lumber yards, etc.

Well, 20 years later and several years of desk jobs, laziness, etc., here I am. I have lost just under 40 lbs now. My goal weight is about 20 lbs away ultimately. I'm doing upper and lower body workouts, just added core to my routine as well....today was first day of that, so any suggestions as to specifics to help there would be great, by the way.

While right now I want to stay focused on weight loss as a primary goal, after about another 10-15 lbs, which I'm guessing should be within reach by the end of March, maybe the end of April depending on how much slower the loss goes from here (this is the lowest weight I've been since my early 20's, so no idea if my body will start fighting me a little more on the weight loss from here on out or not). BUT, once I'm down around 210 lbs (223 now), I want to start switching my primary focus from weight loss to building mass and strength in my arms, chest and back.

So yes, I'll admit it, while I am doing this for my health and to just live a better life, I will readily say outloud that I want to LOOK good too. I have a bigger frame, broader shoulders, etc. I don't want to look like a marathon/distance runner. Not saying there is anything wrong with that, but just not what I want. I want to be more of a "V-shape" if you will.

Question is....... should I start to slowly switch my workouts to aim toward that goal now, or should I wait until I've gotten where I want with my weight first, THEN make the slow switchover?

If you suffered all the way through this post, and then still had the energy to type any advice, input, etc. aftrwards....... THANK YOU in advance. I want to do this right and smart, and like to hear as many points of view as possible.