When it comes to dress-up kits and such, what looks cool or personal preference rules. But internal engine work is all about precision and accurate measuring. Valve spring heights aren’t an exception to that rule, and guesstimating won’t cut it. You need a valve spring micrometer.
When it’s inserted over the valve between the spring seat and retainer (as if it were a spring) the threaded members provide sufficient axial pressure (just like a spring would) to enable an accurate measurement of critical valve spring heights to and accuracy of thousandths of an inch.
Engine internal workings aren’t the area for “looks close enough” guesses — save that for horseshoes; you need accurate measurements to get your ride tight and running at top speed.
Plus, a small $45 investment might get you a tenth at the track, and that’s always worth a shot.