The deadlocks will slow a thief somewhat but the issue with them is that they will only stop somebody who doesn't know what they are doing. And that is mostly nobody at all. The main problems with deadlocks and slamlocks are:
1. The door can still be bent open from the top corner. The solution for this is 'high-level' deadlocks, which are only a little bit more expensive.
2. Fit high-level deadlocks and they will cut open the roof. Seriously. And there isn't much you can do about that!
A solution me and my mates have found is fitting a GPS tracker inside one or two pieces of equipment in the van. If the van or its contents get swiped you simply go directly to where it was taken and 'collect' it. Take the police with you; or perhaps a stick and a rottweiler
Here are the GPS's that we have fitted in our gear.
https://amzn.to/32ifUMk They are the size of a packet of fags and the battery lasts for months. Open a panel on your big drill, groundworks tool, carpet cleaner or whatever and gaffa-tape the little beauty inside. Any time you call (or text) the tracker it sends you a text with its location on Google maps. Accuracy is within 10 feet, which should be close enough.
I appreciate this is not really an answer about deadlocks but I hope it helps with your ultimate issue, which is sleeping easy knowing you've done all you can to protect the tools that you use to support your family.