You had to know that a "perfect engine" thread would get me and Al out of the woodwork. It's like poking a bear-- you're going to get a response, like it or not. This one is not "Teby 2-paragraph approved", but I'll try to stay on point. My wife reminds me that not everybody is entitled to my opinion, but it's difficult to sit on my hands when I'm sure I'm right (even when I'm not). I could be wrong, but I'm not (no I'm not). I'm just a busted up old pipefitter, so take it with a grain of salt.
Let me start by saying, hindsight is always 20/20. Given the cornucopia of options for engines, there are less paths to righteousness than you would think.
I had two cars with 1776s. I told myself, and even made some failed attempts at arguing that the engines nicely replicated the original's power, etc., blah, blah, blah.
Once I decided I didn't care so much about exactly "replicating", a bigger engine became something of a no-brainer.
I've had every permutation of Type 1 back there since-- big drag-racing 2332, exotic twin-plug 2276, "standard" 2110. Of all these engines, the bang/buck sweet-spot is the 2110. It neatly cleaves the middle-ground between maximizing power and reliability.
Actually, that last sentence indicates that you are giving something up from a reliability standpoint with a 2110, and I don't think you are. I know I may get some blow-back on this-- but IMHO, it's about the maximum engine size that will be nicely supported with stock-ish head castings (which ends up being a big deal from a cooling standpoint). Everybody (rightly) says, "the power is in the heads"-- get much bigger, and to maximize the displacement you'll need castings that don't cool as well, welding on stock castings, or both.
CB's new 044 Panchito head is almost a miracle. The flow they get out of it (unported) with the small runner size means that an engine built with these heads will make power from idle to 6500 RPM, assuming the target HP is kept in the 150-ish range. They have very, very open castings for cooling. Coupled with 90.5 Mahles or thick-wall 92 AAs (2180), these would be the perfect starting point for a nice speedster engine. Actually, if I were doing a Type 1 again, it'd be the only thing I'd consider.
Jack's right about Type 4, although the sticker-shock of a nicely built 2.3-ish Type 4 will run most people off. It's definitely a buy once/cry once proposition. That's what I was saying about hindsight. If I'd have known how much money/time/effort I was going to pour into the back of my car, I'd have just bit the bullet on the front end and gotten an engine that fixes all the Type 1 ailments, and gives up nothing (except money). The ONLY touble at this point is finding a builder for hi-po Type 4 engines. Jake Raby still does them, but the pricing has always run off most guys. Greg from FAT Performance is closing up shop. That leaves.... crickets.
Good luck. Forewarned is forearmed.