at the point of no return, now Christopher... 91gal tank to heat... With that in mind, i think yo u definetly need the TiH assy along with the FPHE.

Man, i'm glad i pulled the trigger, 1yr strong now bud, and 25k miles...

As to "purging" / reutrn line, i'm just offering my set-up, not try'n to re-invent the wheel, but mine goes like this....

Tank , pump , filter , 3/8 CV , manifold (2nd pic down McMaster-Carr ), 1 port branched to purge valve.. 7876k68 McMaster-Carr ) , FPHE , TiT assy , another manifold located in valley , branched to ports to p/s front and d/s rear. CV's located on factory fuel line ports.

This is the setup i replicated. I use another barrell in backyard to FIRST filter...
Once its time to purge, i kill the wvo pump, flip my d2 switch, and its purges thee entire system up to the manifold. Purging TiT, fphe.

I think, having a "fixed" psi wvo pump, you utilize not having a return line, regulator..etc.

My systems enclosed in a metal box i made, i can send you pics of it along with pics of other systems i have, that they located items along the frame. Some stupid reason, i can not post pics here..