One of the things that bugs me about many old annual kits is the out-of-scale and, more often than not, inaccurate shape of the vent windows. It might seem like nit-picking but fixing these issues goes a long way to enhancing the appearance of a model and making a funky old kit look better than it really is.
In the case of a kit where the shape of the opening is right (AMT "old tool '57 Chevy, for example), all that needs to be done is to cut a new window glass out of some clear packaging material, acetate, or styrene that’s has a more correct scale thickness, outline it with a BMF “frame” after removing the ridge the kit maker used to represent the frame for the vent window glass and gluing some sheet styrene inside the opening for the new window fit against. The new window is installed from the outside. In some cases, such as AMT's '59 and '60 T-birds, the shape of the existing frame and opening may need to be corrected with some careful knife and file work. Sometimes it's easier to cut the frame out to reshape it, then reinstall.
In some cases the frame is best replaced entirely. All of AMT’s 3-in-1 annual Ford Galaxie hardtop and convertible kits from ’60 through ’62 (and Mercury, ’61 and ’62) suffer from an inaccurate vent window shape that’s too triangular, too “pointy” at the top, and too thick overall. On the real car, the vent window frame and glass have a small flat section at the top and the rear vent frame and window channel, rather than being vertical, is angled back a bit at the top. Additionally, none of the hardtop kits have any representation of weatherstripping or window channel for the rear quarter window.
On my rebuild of this original ’61 Starliner I decided to make new scratch vent window frames and add some strip styrene to represent weatherstripping and the channel for the rear quarter glass. Using available photo reference and a pattern taken from the model after the old vent window was carefully cut out, a new frame was cut out of some sheet styrene and carved, filled and sanded to shape. The ridge inside the frame was made by cementing thin sheet styrene to the back of the frame and cutting out the opening, leaving the thin ridge for the glass to sit on. The rear vent window channel is a separate piece.
Some refinement is needed, but here’s the driver’s side thus far. I'll try to add more pics of the process when I work on the passenger's side and finish up the driver's side.