After seeing Ben Fulcher's 1/48 Privateer at the OKC contest (which took home some bling from Nationals as well), I was inspired to pull out my Matchbox 1/72 Privateer. After looking it over, I ordered replacement "glass" sets from Squadron, resin engines and nacelles, and Quickboost gun barrels. When I started work on the turrets, I realized just sticking the Quickboost barrels where the Matchbox broomsticks were wouldn't suffice - I needed to build out some detail to the turrets themselves.
Here are the parts I started with for the 2 top turrets:

With the replacement turret, I needed to cut the Matchbox clear part in half and use the bottom half. I filled in the gun slots, as they do not extend down as this part has it. I also thinned the remaining section as much as I could and still get it to fit on the base, so I'd have room to build out details inside the turret. I cut off the barrels, glued the cross piece to the mounts, then sawed the ends off and filed down substantially to make a mount for the .50 cals I manufactured out of styrene. I glued the remaining clear base to the base of the turret, blocked in the slots and painted the interior before I began to work up the turret. I glued the Quickboost barrels to the .50 cal stocks I had built and painted them up, then glued to either end of the crosspiece, after I had seated the gunner. I did need to cut some off of the guns to make them fit, as the space within the turret is very tight. Next I added some additional details with styrene. I used a carrier section of the Squadron canopies to create gunsights. I cut up copper wire, laid it between a couple of strips of crepe art tape and then trimmed, to create the look of a bandolier of shells. The last pic below shows the cut out Squadron turret sitting atop the base - I haven't cleaned it up or detailed it yet, but as clear as it will be, you can see why I felt I should detail out the turrets!




Nice work. Can not wait to watch build progress.
FFL
Here's some work on the tail turret. I decided not to use the Squadron vac replacements, as the shape wasn't what I wanted, and there was nothing substantial to attach the scratch building effort to. So trimmed off some of the front yoke and attached to the clear part, then built out the interior. These pics show everything installed except the gunner (had to steal from the spares box, as the kit didn't provide one).
I'll add another pic or two showing the finished turret with gunner.
Also finished the cockpit area. Added arms to the seats, and engine control knobs and levers, and a few decals to the center console.