For the more popular FF here are some popular and competitive choices w/ 1983 being a good barometer, as this was the year front & rear in-board suspension cars really took the market by storm:
~ Crossle 55+ (used to build all the cars for Skip Barber prior to Mondiale, 30 series are popular Club Fords)
~ Lola 640-644 (Michael Andretti ran factory backed cars in US, Charlie Matthews has successfully autocrossed 644 in CenDiv)
~ Reynard FF82+ (These cars put Adrian Reynard on the map, great parts availability, large cockpits, driver friendly)
~ Van Dieman RF85+ (85 was a Swift copy, which evolved from there, can be tight fit for larger drivers)
~ Swift DB1 (most expensive on list, but also most plentiful, can be tight in shoulders for larger drivers)
~ Citation 85+ (beautiful cars built in IN w/ support still available from ICP. Peter Raymond/Josh Sirota/Jim Garry car has been very successful)
and many more choices available...