You might be able to kitbash something from a Rolls-Royce powered 747-200 kit, those had the same RB211-535D engines as the later L-1011s. Whether the nacelles were the same is something I'm unsure of, but the back ends sure look alike. Maybe combine 747 RR engine cores with L1011 nacelles (thinking aloud here)? Also, make sure you pay attention to the fin leading up to the #2 intake, some of them had a little fairing while earlier birds had a gap between the fuse and inlet before the S-duct.

Depending on the scale and the kit you're dealing with, it shouldn't be that hard to represent. Long ago I updated the engines on a Hasegawa L-1011 to represent the later RB-211s, and did it with some judicious shortening of the hot section and some epoxy putty to resculpt where the hot section meets the pylon. I used photo references to help me, and ended up being very happy with the result. It may not be dead-on accurate, but it looked right, at least.

Likewise, the Frisbee fairing (filling the gap between the fuselage and the #2 intake) on the later and retrofitted TriStars, and the TriStar 500s, isn't really that difficult to add with some plastic stock cut and sanded to the proper shape and puttied/faired in. I had to build up the Welsh kit's rather anemic fairing, but it wasn't difficult either. I don't recall any of Eastern's having the Frisbee fairing, and I can't find any pictures of Hawaiian L-1011s with it either, although I may very well be wrong.

Flying Colors used to offer some gorgeous later RB-211s for the TriStar. I mourn that they're sold out now, and if I had a time machine, I'd go back and buy several more sets.