As far as I know, most of the cars were Lotus 18 school cars purchased from the Jim Russell outfit in the UK and the Windfield school at Magny Cours in France. I remember that well because at the time, I worked at the school and Henry Morrogh and Tico Martini used the money to engineer and build the far more advanced Martini MK1 "Formula France" racers.
The excellent Indycar V8 being an absolutely useless GP motor..
With personal experience of these engines, and compared to the far more successful Drake-Offy, I would like to add that the Ford 4-cam V8 was not so excellent. It was in fact and still remains today, very flawed. It used a cast crankshaft, cast camshafts, and they keep breaking to this day, as what happened to us with the 1966 Eagle we were exercising at California Speedway, causing that car, the very first built by AAR, to spin at a rather scary speed and we were damn lucky to not hit the wall. There are videos of that on YouTube if I recall.
I have several friends with vintage Indy cars with that Ford in it, normally aspirated (4.5-liter) or with turbo (2.6-liter with very short stroke) and they are nothing but an expensive pain in the behind. Basically they need a rebuild each 500 miles if you want them to live.
Yes, they won the "500" several times as well as other races, but they required a far greater and far more expensive commitment, and only a few could make them last.
Compare that to the very reliable Drake-Offy in either normally aspirated or turbo versions, able to spit a reliable 1000 ponies anytime of the day and last over 3000 miles between revisions, and you get the picture.
The Drake-Offy finds its ancestry in 1931 when a Miller "marine" engine was put to work in an Indy car. Fred Offenhauser purchased the assets of the Miller company in bankruptcy, and the "Offy" was born.
The Ford 4-cam was of course based on the Fairlane road-going engine, now cast in aluminum and fitted with 4-valve cylinder heads copied on... the Drake-Offy.
So Bruce McLaren made a wrong choice when pushed to develop that 3-liter boat-anchor of an engine especially considering the bulk and weight of the Ford. Things got better later, fortunately.
Dave's little car is a splendid job of carving, lovely little machine.
The excellent book by Howden Ganley, "Road to Monaco", tells the story. I highly recommend it.