your requirements are almost identical to the two Duratec chassis that I have ordered in the past year. they were based on the R400 chassis, diff mounts strengthened, lowered drivers floor, removable RH engine bay diagonal, short passenger footwells the only biit not applicable to your spec is the modified lower engine bay chassis rail which would only make your installation easier. This chassis also comes with the hydraulic clutch master cyl. You will have to be quick if you want an Arch chassis, may have to beg.