What would anyone recommend for an Indy/Pinto tyre pressures for normal/fast road driving?

18-20psi..

^^^ That seems to be around the norm for our types of cars

Mind though it depends on how wide the tyres are, like my 600kg beach buggy is just 15psi due to the huge width of the wheels. A simple way I check is to clean the tyre, then drive it over some dust, gravel, powder etc to see how much of the tread is in contact with the road. If the centre of the tread is lightly or not covered then you need more pressure, or the edges of the tread are lightly or not covered you need less.

i run at 18 psi with my pinto, compensate for the extra weight

At 18psi mine drives like a heroin addict, at 22psi front and 26psi rear it drives like a dream. tyre wear is even, over 10,000 miles later. It weighed 700kgs at SVA which may make a difference though.

the handling of mine on the track improved with every extra PSI I put in. I settled at 20 in the end.