Luckily, there are a ton of options for the early Mustangs. From upgrading your stock front end to complete replacement suspensions. If you're on a budget and need the car to be drivable then modifying the stock front end in stages is you best bet. If you can be without it and can drop a little extra money(at one time) then complete replacement is a good option. Just keep in mind that doing it in stages can end up being more expensive than the one shot deal.
The vintage-mustang.com website is a great resource.