Paul Stacker from Stacker Motorcycles had some old Wiseco piston kits for '73/ '74 Husky 400s at the CD4 swapmeet, in .060" & .080" oversizes ( which might be as big as the bore size you need for a 450). They were fairly cheap too . I don't think that the old style Wisecos are as good as a Mahle or a new Wiseco prolite piston , but it might do the job. Stackers phone number is 0394599535 & might be worth a try.