4bt 72 Dart

I have no personal experience with a blown out front seal on an injector pump nor do I know anyone who has experienced it so I'm only parroting what I've read on the interweb, it could just be misinformation that's getting passed around but if the front seal does happen to get pushed out it's going to fill the crankcase with fuel and you won't know it until you check the oil or it starts knocking, so not a good situation. The stock lift pump for the VE injector pump puts out 5 to 7 lbs of fuel pressure, the lift pump you have on there puts out about 4 times as much pressure.

Same thing goes for the killer dowel pin on these B series Cummins engines, I've never seen one come loose in person, I've seen pics of the aftermath though, I have personally seen timing case bolts that were loose which if left unchecked will destroy the front cover and gear train. It would be worth it at this point to pop the timing cover and check these things at this stage of the build while everything is accessible up front. Also check the timing gear for cracks while your in there, I've had that happen to my 6BT. Another "while your in there" mod which I've done is to "pin" the front seal into the injector pump to keep it from walking out, this involves drilling and tapping 3 small holes around the seal parallel to the shaft and installing 3 button head screws with some locktite prevent the seal coming out.

These are good little engines but expensive when they break so an ounce of prevention is worth a couple of pounds of cure in this case.

The Hungry Diesel.com sells a low pressure piston lift pump for the VE injector pump and I believe sells a weaker spring to lower the pressure. I know your build is for mileage but the fuel pin and 3200 rpm governor spring upgrade really wakes these engines up, just have to keep your foot out of it to keep mpg's up.