Does it matter for a car?
They MIGHT start a car in summer when new. But gel batteries dont have high cranking amps. The 74Ah MK gel, can do a max peak output of about 380 to 405A depending on temperature. Best in summer... Thats not cranking amps over time, thats just peak. Which is why you cant find a cranking amp figure for them. Do it for long and blow bubbles in gel. That will work to start a typical car when new in summer just.
The PC1500 Odyssey can do about 5000 Amps max peak without damage, and 1500 Amps for 5 seconds which is a long time if you count from zero. Much longer than needed to start a motor. Thats why they are used in auto sport, so a smaller lighter battery can be fitted and still start a big high compression motor. Or a truck in a siberian winter.
So they are likely to be dissapointed. You would need 2 or 3 MKs/Sonnenschein gel batteries to replace a high cranking amp starter battery.
The odyssey can do BOTH deep cycle duty, AND yet
out perform a high quality starter only (SLI) battery. Along with YELLOW Optima. Both with very high cranking amps. The optima is less good for our purposes though.