Will this hose work for both coolant and vacuum lines?

Yes. Silicone handles coolant, vacuum, and even mild boost without degrading. Just confirm your application pressure stays within silicone's limits before install.

Do I need clamps, and what size should I use?

Hose clamps are sold separately. For a 3-inch hose, grab standard worm-gear or band clamps rated for your line pressure — check your vehicle's service manual or existing setup for the right fit.

Can I cut this hose shorter if I need a different length?

Absolutely. Silicone cuts clean with a sharp utility knife or hose cutter. Just seal the cut end properly with clamps when you splice it into your system.