my h1 500 was a 71. was racing it a strip every sunday. fastest thing i had to outrun was the cb750 honda 4 with 4 straight short pipes which they all ran. funny u mention someone paying fro mods, i won about enough money to pay for the h2 750 basic bike in a year street racing those 750's. kept my z1 900 stock about a year, then 1015 yosh kit, full yosh head, 417 megacycle cams, 31 cr amal gp carbs, denco header, and lightweight snowflake magnesium kimtab wheels. pro stock racing was brand new, my friend mike bruso lived 25 miles from me, he put my motor together. he held original pro stock record at 10.0 my bike with him rding would go 10.60. yeah, i was serious back then, damn 47 years ago. btw that kz was not beyond a tankslapper either.