I am building the 1968 Coronet R/T convertible kit right now. This is a clone of the original 1968 kit, and as such, comes with a pretty simplified chassis plate. I found that, with a little trimming of the firewall and radiator support outer edges, the more detailed chassis and powertrain parts from the 1970 Coronet can be substituted for a more detailed build.
Since this is supposedly a new set of tools to produce this kit, I am surprised and a little bit disappointed that Round 2 did not do the same thing, using more detailed chassis parts. They already own the tools to do it.