Which motor Shield for these Actuators?

Ok I just looked at the whole thread and dont see a link to your "h-bridge" so please post a LINK.

As for reverse emf etc then until I can see what you think I can see then I cannot answer.

The crowduino is pin compatible with regular UNO's etc so if it is a shield then you should be able to just pop it right on top.

EDIT... My apology....Yes that one will drop right in and has its own supply terminals so will not be an issues with back emf etc.
It is also quite beefy as these things go and has a little wiggle room too with up to 20 volts and the extra amps.

You may find ones similar also on Ebay etc.

Search for dual mosfet but make sure you avoid anything that says IRF520.
As i stated earlier I use IRF540 modules quite a bit but as also stated by Wawa a logic level version is more preferable.

You will notice the extra MOSFETs on some boards and that is to allow the extra amps to be spread better so they are generally preferable when dealing with bigger amperage items.
AT least until you go crazy then all bets are off.

Sometimes you may be better with the seperate board too to give better access to unused pins for extra goodies.

ok i decided to go for a BTS7960 motor driver. I thank you again for all the help

By the way I got an answer from the company who makes these actuators, and the current draw is 5-6 Amps not 3.3...