I recently did them on my ’92 4.0 (first time replacing injectors on any vehicle, somehow). Should be the same concept. My Haynes manual recommends inserting them into the fuel rail first, then slowly seating them down into the top of the engine. I didn’t know this (because, you know, I’m one of those guys that doesn’t read directions).
So I did things bass ackwards, because the top of the engine was disgusting and even after I had blown/cleaned it off, there was still a ton of grit and oil around the base of each injector. I was worried that some crap would fall down in there while I was trying to line all six injectors up and end up scoring a cylinder or something, so they went in the fuel rail first.
This would have been fine, but the o-rings on my new injectors were really loose and one of the front injectors couldn’t be seen during installation, due to the fuel pressure regulator being in the way. Things held up well for about 3 days, then it started dumping gas, because the o-ring on that same injector had been torn. I put all of the old o-rings (which fit much more snuggly) on the new injectors, dropped the fuel rail back down onto them (paying more attention to that injector up front this time), and voila! All good.
So I’d say that you could do it either way, but the manual calls for putting them into the fuel rail first, probably because it’s easier to line up the bases than the tops.
Good luck.
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