Stage 1
 

Has anyone bought the Stage 1 kit for the 3400 from Milzy Motorsports? If so, what power gains would I expect from it?

You talking about the stage 1 performance package with the heads, cam, U/Lim, pcm...

Or are you talking about just the stage 1 pcm?

Yes, the performance package with heads, cam, upper and lower intakes, PCM. I was also going to add a 65mm throttle body and a Wizaird cold air intake.

I'm going to say it's definitely not worth the cost, and I also didn't know Milzy was still in business

You might be able to source a 3500 top swap for much cheaper and it should give you some good HP gain in the upper RPM bands

Would a full 3500 swap also be a better option? If so, will the 3500's heads line up with my exhaust manifolds or will they need to be changed as well?

I agree 100%. I am a bit surprised they don't have even ballpark power gains listed on the site. I get tuning plays a big role, but it would be nice to give a general guide.

Realistically though, stage 1 is like $2k (+ core). Add the TB and CAI and you've got another $500. Add gaskets, fluids, shipping, etc and you've got basically $3k in mods there assuming you do all the labor yourself. I'll admit I don't know anything about these parts, but I can't imagine that setup would even do 200 whp.

For that kind of money I'd be looking into an engine swap, boost, or putting it towards an LS fbody since that's easily 1/3 of the price.

A 3500 swap would probably be a better bet then for the money.

Alternative to Stage 1' ing the 3400: 3500 swap with 65mm throttle body, EGR delete, and Wizaird cold air intake. Thoughts? Better HP/$ ratio better?

If you are doing a FULL engine swap, then why not just go 3800?

Not sure how accurate these Wiki's are for the specs on the different engines:
https://en.wikipedia.org/wiki/GM_High_Value_engine
https://en.wikipedia.org/wiki/Buick_...7_Supercharged

But, from what I understand, yes a 3500 makes more power and torque than a LA1 3400. But if you are talking full on engine swap, you are probably best investing in a 3800. A 3500 as I understand should be a pretty simple swap (such as the mounts should line up, the exhaust manifolds should line up without issue), but you will need a throttle body and an adapter to switch from drive-by-wire to cable linkage. You will also need a custom tune on the PCM for a 3500. You also need to retain your current ICM and coils.
All this for an engine that is still not making as much power as the L36 and L67 (which have other various mod options). Plus there are multiple threads here and across the internet about doing a LA1 to L36/L67 swap.

On the flip side, I am sure a 3500 has other modding options to consider, plus it might be easier to get a low miles 3500 vs L36/L67.

If I were considering an engine swap on an LA1 in a Monte, I would probably go L67.
Now, in a Grand Am, different story. In those cars, it IS possible to put a L67 in them (takes some custom work), but I would probably consider a 3500 for convenience of the swap (less custom work).

Just some ideas to think about.