My 72 has M14 x 1.5 thread wheel studs (although it is 4 stud, not 5).

According to this website, you should have about 9.5 turns of the nut

https://www.drivenproducts.com/blogs/wheel-and-wheel-accessory-terminology/minimum-thread-engagement

1972 4/4 4 seater, 1981 MGB GT
1984 Harley Davidson Electra Glide, 1990 Kawasaki ZX10