Probes aren't real expensive. Don't forget that you can probe every cylinder if you want to - just have to use an 8-position rotary switch to choose which one to read on the gauge...

Gaffrig makes a dual gauge with 2 needles in it that is cool for a Vee motor - one from each bank. (or one from each motor).

YEAH YOU CAN WATCH EVER CYLINDER BUT ITS JUST TO MUCH TO WATCH !!!
I AGREE WITH BLOWN1500 WATCH NUMBER 6 ,PLEASE ,IT WILL SAVE YOU A MOTOR AS IT HAS ME ON SEVERAL OCCASSION !!!!
SEE YA ,MARK USE THOSE WRENCHS !!!!
BOBBY