A little more progress to show. The core block is ready for some polishing.

And the driver side plate is almost finished. Have to add the door handle and a little trim around the reflectors.

Notice how the roof part is higher than on the Mercury. I tried to run the seam where the vinyl top would have gone on the Merc but it is hard to trim the flash in that spot. This Plymouth has a vinyl top over only half the roof so no need to match that seam. I parted it higher up on the roof where the mold line would be easier to smooth.
A couple other things I am trying to do. There are no location spots in the underside. They were causing me sinking problems in the Mercury as the plastic cooled and contracted and really they are not that important.
Playing around with the mold design for the remaining parts and also trying to produce a more race style interior with roll cage.
The rear spoiler is going to be on the sprue if at all possible but there are no location on the car. I figure if you are a scratch builder you can make a guesstimate where to attach the rear pedestal spoiler.
Working on all 3 hoods to include if they will fit.
I need to do a little research on the wipers. On the Merc the wipers vanished behind the hood when not in use. I think this Plymouth was similar, but I could mold some wipers on to the front glass if they were visible.
The side mirror is not decided yet. I may copy an old 1970 Mustang kit from Revell where they had a protrusion that glued on the inside. I have to make that decision extremely soon because this side is almost done and if I need to put a post there I got to get to it.
One thing I greatly dislike about my normal slot cars I buy is how flimsy the side mirrors are. They usually end up lost within a few laps. I know I could remove them before racing but I already have a bag of mirrors collected from around the track. I do not want to have a spare parts bag for every car.
So if I am doing side mirrors they have to be solidly glued on so they do not come off in an accident.
Ok, so this is about 6 of the 16 steps finished.
Will post more pics as this project grinds ahead.