The theory is that the centred FPR in the later cars was to more evenly distribute the fuel. However, you could probably find a great many people with the '70 and '71 setup that have awesome running cars. Some of which may never really have done anything to them ever. The D-Jet is such a low-tech system -that keeps it pretty easy to stay on top of problems. Not to say it won't baffle us from time to time.
I've had FPR's dry up and clog up and not work though-with symptoms similar to yours. Most likely from lack of use. Rarely happens though. You can still find them fairly cheaply if you keep an eye out.

Using the FPR or your injectors as a filter is essentially what you'd be doing by having deteriorating fuel lines in front of the proper filter. Rusting lines, crumbling rubber hose, holes acting as a vacuum sucking in road grime. Nah, I'd say new lines is a small price to pay for not becoming Johnny the human torch.

Cheers