Not sure of the year of your truck, but on my '06, there is a plug on top of my main filter head that can be removed and a hose installed to the by-pass filter in fitting. The out fitting would go to a swivel head installed in your oil fill cap. Or you can buy a fill cap that is pre-drilled for this purpose.
Now, I have viewed the website, and three things they don't say that bothers me.
1) How much for the unit ?
2) what are the filters made out of, toilet paper rolls ?
3) How much for the replacement filters ?
Oh and add this, if what they claim is good, where are the independent lab reports they have that you can obtain and test if you want ?
I'm sorry, I couldn't find these ?
If they have been around in England for a while, shouldn't they have there act together for the website to have these answered ? Are the British consumers different than here not wanting to know these simple questions ? I'm not saying they are crap, but as a consumer, I'd need more than having to call them to a sales pitch or giving them a chance to get my phone number or email address. There are many systems to choose from, I would need more from them to decide or change.