Hi Aerobat,
I can't help much with the "G" side of things, but...
Working from my understanding of the EAA and Peterson FAA STC's for Mogas use. and the Canadian blanket approval which followed, I will offer the following thoughts. These are not exhaustive, as there may be more recent information of which I am unaware...
The FAA STC's should be expected to state a requirement for US (ASTM) standard Mogas. Expect that other nation's or standards for Mogas might not be accepted as compliant with the requirements of the STC (so check this first). This is the problem we originally had in Canada, as our Mogas is to a CGSB standard, not an ASTM. A friend and I created a legal work around for this in the day, but that was 20 years ago, and the spotlight seems to have long faded from this issue in Canada.
That said, if it is an Aerobat you are considering, you may find that the STC does not include it, so, again, check before you buy. The reason is that the Aerobat has a slightly different fuel system. In my opinion, the difference is entirely non-important, but it was a difference which distinguished it from being approved in the early days - perhaps it is now. The O-200 is perfectly fine in either version of the 150.
All that said, if you can make it legal, expect delightful, and economical operation if a 150 on Mogas, particularly in light of the pending removal of 100LL. I have 23 years, and 2400hrs operationon Mogas in my C150M, and much more Mogas time on other aircraft too. It is the ideal fuel, and far superior to 100LL in many respects. It does demand some operational caution, but any engine does! I do recommend a carb air temp gauge be installed.
I have previously posted quite a bit here about operating 150's on Mogas, so I won't repeat it, unless you tell me you'd like it, and cannot find it with this lacklustre search function...
Also, enquire if you can get some road tax (buried in the Mogas street price) back. At present, I get $0.12 per litre back, once I prove the Mogas was used in a plane - not a car. That helps keep the cost of flying down a little. Expect to encounter some opposition from airport authorities about fuelling with Mogas, and be aware that there are many hazards with transporting, and casually fuelling with Mogas. It is very much better served pumped through a proper filter, from a diked, properly installed, and grounded tank, with a bonding wire to the aircraft being fuelled. Jerry canning any fuel has a lot of safety issues, and should be an infrequent means of last resort, not the norm.
Good luck...