Wouldn't underestimate the costs of restoring a 1970s era valiant. By now, that engine is probably nearing 40 years of age. Think about a car or truck engine that old!! Repower on a yacht like that is probably easy $15k.
Rigging may look good, but I've seen more than one blog of catastrophic failure of chainplates on older Valiant...or not the chainplates, but the knees themselves. All appeared fine on the surface, but the issues were subsurface cracking and substandard metal. On a 40 year old boat, those should be replaced anyway...they've well outlasted their useful life if original.
Why look at the low-end of the market? Why not try and cherry pick a valiant thats gone through an extensive re-fit at a reputable facility and has had owners plans that have changed. A boat like this (or similar like Baba/Tashiba/Panda, Pacific Seacraft, Nordic/Norstar) comes up about once a year. Just be ready with cash to pounce on it with a near full price offer!