Some people have good results with clamp-up. The clamps are a little un-slightly if you are picky about looks. I have been installing Time-Valve systems for over 40 years. Sometimes I have to use a torch to make some slight adjustments (front pipes mainly). I like these systems. There are some issues you will have to deal with. The tail pipes are slightly undersize, so your chrome tips will be a bit looser. A screw or crimp can fix this. There is no exhaust gas cross-over built into the front pipes. Lastly if TimeValve sends you the connector pipes (between the muffler and resonator) welded to the center muffler. They will be backward. I always request that they not weld them as per original so I can weld them in correctly. With these connector pipes installed backward, the pipes come closer to the rear tire than usual. About half the cars out there have the connector pipes installed backward. Not a big deal, still works, just not right. The exhaust note is slightly different. Most owners do not even notice the slight change. Disconnecting and re-connecting the front pipes at the exhaust manifolds is the most tedious and difficult part of the job. Get new bolts and nuts. Don't forget the new seal rings and hangar rubber rings. Make sure you have all the correct steel hanger brackets. Bad installations will cause squeeks, rattles, vibrations, fumes and ruin the drivability of the car. Those expensive heat deflectors (asbestos flats sheets) protect the rubber hangars from exhaust heat. Pay attention to all clearances, especially where the muffler clears the rear lower quarter panel. The exhaust pipes should be parallel with the rear bumper in back when done, and should not stick out too far. The front pipes cannot be installed unless the car is tilted 45 degrees or unless it is at least 48 inches off the ground. Otherwise you may have to take the starter out first. Big job. If you install these systems correctly, you will never have to do it again.
