I'd take an LSD-equipped 5-speed F35 (the G85 option) over a 6-speed F40 without it.
I completely agree. LSD equipped cobalts are even harder to find than a cheap LNF cobalt. I'll definitely want an LSD and from what I've seen this is another reason to go with an F40. A Quaife LSD for the F40 will run you $1100 shipped and is much easier to install compared to an F35. You could get an OBX LSD for the F35 for around $400 although you'll need a bunch of specialized tools to get the job done and material cost will probably run another $50 - $100. I watched an F35 disassembly video someone put on youtube and it was really involved. Probably better to pay the $1k+ to have it done at a shop. The Quaife LSD for an F35 is going for $1100 + shipping from the UK so you're certainly not any better off if you want a Quaife.
Another thought on the LTG engine, it was developed as a RWD motor so the mounts for the engine and the accessories may be very different or non-existent.
I was thinking the same thing, and while I wasn't able to confirm the FWD and RWD LTG engines blocks were the same, I did find a few places that talked about the oil pan being different between the two versions. It sounds like the LTG is around the same size as the LSJ/LNF/LDK, although it doesn’t share the same mounting points as the older 2.0 ecotecs. That said it does appear to share the same bellhousing bolt pattern as all other 2.0 ecotec engines.
If you were to go with an LTG you would certainly need to engineer custom brackets and potentially modify the cobalt subframe.
Why not get the cheapest cobalt you can find for the random bits like pedal box, steering etc and then get a Saab 9-3? They are dirt cheap and you're going to need all the electronics out of it anyway. If you get an eBay motor and trans you won't get all the wires needed.
It would give you a turbo ecotec and F40 already mated, although from what I've seen the cheap 9-3s on craigslist all have a bunch of miles and only have 210 HP, 220 ft/lb max. Might be better to stick with a LSJ with similar mileage. The wiring issue would be another challenge/hurtle. Getting a used ECM would be easy although figuring out to get everything working would take some patients, time, and probably a crap-ton of googling.
Looks like the LT swaps sides for the intake and exhaust. That'd be a real challenge to fit into a Goblin.
You're right the intake/exhaust has been switched, apparently to be better suited for longitudinal engine placement. This might be the biggest hurdle. I haven't been able to find any examples of how to route the exhaust and turbo pipes in a Goblin-like setup. There is a
similar post on a Fiero forum that talks about this being an issue although it doesn't look like anyone has attempted it yet. Someone also posted a
link to a great description of the LTG engine and why it's better than the older Ecotec engines. Other than the low miles and price of used LTGs that is.
After reading up on everything for the past couple days it's looking like a cheap LSJ is probably the way to go for a Goblin build. A DIY turbo swap wouldn't be impossible and would hopefully cut the $5k ZZP price down to $2k ish? I don't see anyway around a high mileage donor motor other than buying a brand new LHU long block on ebay for $3100. Which would be a pretty good option if you found an LNF cobalt donor with a blown motor.
As far as a transmission goes the F40 certainly seems like a winner from an LSD, reliability, and gear ratio point of view. Although I haven't found a clear writeup of how to adapt the F40 to a Goblin/cobalt setup. ZZP used to offer an expensive kit but it doesn't look like an option at the moment. Seems like a waste to put $2k+ into a used G35 for an LSD, when a new F40 + LSD can be had for around $2100 if you install the LSD yourself. I might get lucky and find a donor with an LSD already installed but I'm not holding my breath. I'll need to learn more about why the F40 won't mate up with a cobalt. Maybe it'll shed some light on how to make it work.