This is going to be an expensive bike unless you buy all your parts used as well.

Also an '86 is a frame design from back when the frame geometry was intended for short length rigid forks. The frame is not intended for use with suspension forks. If your plan is to install a suspension fork then you'll be limited to only the shortest travel forks out there. That would be the 65 mm cross country travel forks. Anything longer will raise the front end and make the steering geometry feel very "confused".

If you're just after a utility bike for in town errands or you're looking to create a nostalgia off road bike then you're on the right track. But if you're looking for a bike that will be a solid off road performer with a good mid length travel set of cross country forks, like an 80mm fork, then you've bought too old a frame.

Your old frame will likely have a 1 inch steerer tube on a threaded fork. Again this will limit you in your options unless the goal is to build a "vintage" style cross country mountain bike using the old tech parts. If it does have a 1 1/8 steer tube fork then at least you can fit it with a 65mm short travel XC fork using a threadless headset.

Beyond that your question is so open ended that a suitable reply would require a whole book length post. What you need is some further background in what the options and typical parts are that you'll need. There's three sticky thread at the top of the forum listings. I suggest you read through a lot of the sites that are linked for some solid background on what was used from back then, what options you have for using current stuff on such an old frame and a lot of how to do this using the Repair section at Park Tools. You'll get far more first hand help that way than what we can give. It will also help you to figure out what specs your own frame has and to determine if it restricts you in some ways that make this project a non starter.