Well, may be your lucky day. I have 3 ISBe engines on my Quick Serve. The first 2 I checked have the same intake as your engine. The 3rd one has that style you're looking for. I'll give you the part numbers in the order they appear on the diagram. Some of the parts like bolt you may reuse but I'll list them anyway. This part was on a ISBe 4.5 but I assume it should bolt to the 3.9 head.
I suspect you may need smelling salts when you price this creature.
1. 2830693 Intake Manifold
2. 3901446 Flange head bolt M8x1.25x60 1 required
3. 3918109 Flange head bolt M8x1.25x25 6 required
4. 4894046 Plain flat washer 1 required
5. 4894048 Plain flat washer 2 required
6. 4894727 Engine Heater
7. 4895488 Lock Nut 3 required
8. 4896355 Retainer Cover 2 required