Aside from block and cylinder head bolt similiarities (which are more "general" than specific really), the heads have nothing in common aside from intake/exhaust valve layout and Ford didn't use that style of intake for quite a long time. They also have the benefit of 6 bolt mains and not cracking down the valley at high HP with stock blocks.

Nothing against Ford stuff, and there is definitely some design "style" borrowed for the LS stuff, but it's pretty far away from the 289 and its descendants.

You can bolt up Ford heads to the LS1 motor, the heads are a direct copy of the Ford 390 heads, and the intake is a copy of the Ford 428 Hi Rise. In the LS1 the oiling system, the cooling system, the intake and exhaust ports, even the amount of head bolts is directly from the old SBF. Even the distributor is even now in the front if you went carb/distributor setup. And now the LS1 even uses a SBF HO firing order. I'm sorry, but anyone daft enough to think this isn't taken right out of the pages of the SBF that's been around forever is an inbecile or, like many, don't know anything about their competition's products because they've never built one. From someone that has done both, it's plain as day the LS1 is GM's version of a SBF. Rumor has it that a Ford engineer quit during the design of Ford motors in the late 80s, he was in charge of a new pushrod while another team was in charge of the new Modular series of engines, the Mod motors were chosen and the engineer quit. A few years later GM released the LS1. Due to it being more than 2 years later Ford couldn't legally do anything, but why would they? Ford was pushing a more reliable engine with a smoother powerband that promised more power per displacement along with an easier assembly between different displacement motors. GM had a motor that, at the time, was being phased in very slowly by comparison. If it wasn't for Holden of Australia the LS1 would have never evolved past the initial design.

Either way both are great engines. However, the Ford small block has gone mostly unchanged since it was created and parts are cheap. Also, almost any shop can work on a SBF while the LS1 has been discontinued.