Hi Ralph - welcome to the forum!
Before Scalextric produced Digital Plug Ready cars, there were a small number of cars that were chipped in the factory. Almost all the other cars produced - including all the classic Le Mans models - could be converted to digital using the C7005 (F1) or C7006 (saloon) 'retro-fit' chips. There were no classic Le Mans cars that I know of that were factory chipped. Nowadays, the C7005 chip is the only Scalextric 'retro fit' chip available and it is a fairly straight-forward job to convert any Scalextric car - requiring basic soldering skills.
Looking through the old catalogues, there are a lot of Scalextric models of cars that raced at Le Mans in 1966 and 1967. Starting with the most recent...
- C4031 Ford GT MkIV #4 Hulme/Ruby 1967 (DPR)
- C3951 Ford GT MkIV #3 Andretti/Bianchi 1967 (DPR)
- C3893A Ford GT MkIV #1 Gurney/Foyt 1967 (DPR) part of twin pack with 2017 Ford GT GTE
- C3630 Ford GT40 Scuderia Filipinetti #14 1966 (DPR)
- C3533 Ford GT40 Rindt/Ireland #12 1966 (DPR)
- C3315 Ford GT40 Ligier/Grossman #15 (non-DPR)
- C3097 Ford GT MkII Andretti/Bianchi #6 1966 (non-DPR)
- C3028 Ferrari 412P Attwood/Courage #23 1967 (non-DPR)
- C3026 Ford GT MkII Donohue/Hawkins #4 1966 (non-DPR)
- C2918 Ferrari 412P Rodriguez/Barghetti #25 1967 (non-DPR)
- C2917 Ford GT MkII Hill/Muir #7 1966 (non-DPR)
- C2683A Ford GT MkII Whitmore/Gardner #8 1966 (non-DPR)
- C2642 Ferrari 330 P4 Mairesse/Beurlys #24 1967 (non-DPR)
- C2641 Ferrari 330 P4 Scarfiotti/Parkes #21 1967 (non-DPR)
- C2578A Ford GT40 Revson/Scott #59 1966 (non-DPR)
- C2529A Le Mans 1966 1-2-3 weathered triple pack (non-DPR)
- C2509 Ford GT MkII Gurney/Grant #3 1966 (non-DPR)
- C2465A Ford GT MkII Bucknum/Hutcherson #5 1966 (non-DPR)
- C2464A Ford GT MkII Miles/Hulme #1 1966 (non-DPR)
- C2463A Ford GT MkII Amon/McLaren #2 1966 (non-DPR)
I'm pretty sure that is all the 1966 and 67 Le Mans models that Scalextric have produced in recent years. There are a few gaps that could be filled - the Chaparral 2F that Scalextric produced did not appear as either of the two 1967 Le Mans cars - the 2F was DPR. A DIY re-livery would be possible. The yellow #2 McLaren/Donohue MkIV from 1967 has not been released yet (although the yellow Sebring winner has). The 1967 MkIIBs are a different shape to the 1966 cars and I suspect Ford would want new tooling to be produced for an accurate model. Looking through the entry lists, there are a couple more GT40 (MkI) cars from 66 and 67. The Gulf cars from 1968 and 1969 are all available as DPR models. Finally, there are a couple more Ferrari 330 P4 and 412Ps that could be done - the #19 factory car and #22 Filipinetti car from 1967.
I hope that's useful to plan your grid. It was fun looking back through the fabulous classic Le Mans models Scalextric have produced.