Several ways you can do this:
1) cut the plastic line at a suitable location, slip hose over it and clamp it and feed the hose to the filters, then remove the other piece of plastic line and from the filters run another hose to the steel line on the frame where the plastic line you just removed was.
2) remove the entire plastic line from the quick-connect fitting on the tank selector valve (careful razor blade action required) and from the steel line, the run a hose from TSV fitting to the filters and again another hose from the filters to the steel line.
Your filters are likely Wix 33195 (NAPA 3195) and are 10-micron filters, if you have 2 of them inline I'd suggest that your replace the one closer to the tank w/ a coarser filter - give Wix 33472 (NAPA 3472) a try, it's 14-micron filter w/ built-in water separator and it should fit the heads you have well (test it tho, don't just take my word for it). In the off chance you're running a pair of Wix 33519s (NAPA 3519) that's a 12-micron filter, and you can possibly use a Wix 33616 (NAPA 3616) 20-micron water separator as a primary for it.