Wheel weights by themselves may not be suitable for many uses without adding a bit of tin or antimony. Linotype is an almost perfect mix but since the advent of computer printing instead of type-setting, it's getting almost impossible to find. Another issue is that so many of the wheel weights out there today are made of other materials. Some states now ban the use of lead in wheel weights and some of the substitutes will ruin a pot of lead if you get just one in the mix. If you have the time and knowledge, lead can be found in a lot of places - ballast in old sailboats, old roofing liners and plumbing, medical radioactive isotope shipping containers, etc. Or you can skip all the gathering work and go to some of the suppliers who sell certified ready-made alloys just for casting.
I buy reclaimed range lead as it's hard enough as is to make good bullets. If you don't have a source, contact Rotometals. They have a full line of ready to cast hard alloys. They also have reclaimed lead shot which I use in shotshell reloading.