You need the OTC 4V cam timing tool kit. It has all of the factory tools in one kit that you'll need. (OTC makes Rotunda tools, which are the factory Ford tools). Price varies, but here's a couple very good websites to check: Sears, tooltopia, usatoolwarehouse, ebay. As I recall, I think I got mine from usatoolwarehouse, but I think Sears might have been cheaper (to much surprise). Usatoolwarehouse sells them on Ebay as well. I love them guys... so cheap for great tools!
There should be a tool for holding the 2 cams together, to keep them from moving. Then, there's a tool for holding the crank in the right position. Then, on the back side of the camshafts, there are some D shaped slots, that a tool fits into, that lines that cam up. As I recall, it lines both cams up at the same time. Before you disassemble the motor, you probably should turn the motor over to TDC on cyl #1 (passenger front cylinder). This way you don't have to time everything from scratch. By the way, be careful not to use any tool with much force in the back of those cams. Those D shaped slots can turn inside the cam apparently, so use them for alignment, not for cam rotation.
In a job like this, if you are just replacing the tensioners or guides, you could probably just lock the cams using any DOHC cam locking tool that prevents the cams from turning, pop off the tensioner, change the parts, put the tensioner back on, and retension it. But using the factory cam timing tools will keep you from making any costly mistakes, plus allow you to set timing from scratch, not just hold the cams.
A couple things you might need to know: crank bolt and cam gear bolts are torque-to-yield. You cannot reuse them; ARP makes reusable and stronger replacement bolts; timing cover gaskets are never reusable; other gaskets generally are reusable; factory cam timing settings and actually degreeing in the cams are 2 way different things; it's a total mother to degree in 4 cams; I've done it; you can't bend valves if you take off the factory cam followers; there are 2 different valve spring compressors required on a 4V to take off the cam followers the factory way; they're over $100 each; you can accomplish the same thing with a screwdriver if you have to; doing this job right, you shouldn't really need to take the cam followers off if the cam timing does not move.
Here's a few pics of my 97 Cobra timing chain setup:
Both cam timing tools. I think the 4V tool is OTC 303-452. The 2V tool is much more common to find on the internet, and it works on the exhaust springs of the 4V, but you need the 4V tool to compress the springs on the intake side on 4V motors. The internet is really unclear at first, when you try to find these part numbers for these tools, which is why I find it important to pass that on. Again, you can probably avoid having to take off the cam followers entirely if you get the motor set up at TDC on the intake stroke before pulling the timing components off!
Back of 4V cam (lineup indentions). RI-SN stands for Right Intake - SN95. (SN95 is Ford code for Mustangs)
Front of 97 4V motor...
4V timing tensioner. Note the ratcheting tensioner that ratchets out as the chain stretches. Also note the hole in the tensioner. Once you compress the tensioner, and recompress the little plastic ratchet tensioner ladder, you put an allen wrench in the hole to hold it all together. When you reassemble, the last thing you will do is pull out the allen wrench, springing tension onto the chain.
You'll also need a power steering remover/installer to get off the PS pump pulley on mod motors. You'll need a good torque wrench for reinstalling the crank pulley. Be SURE to reinstall the crank trigger wheel before putting the timing cover back on. Notice how everything comes apart as you're disassembling. TAKE NOTES! Which was did the crank gear go? Which way was the trigger wheel facing? Etc.