that looks like an aussie 250 2v head, and as i recall is uses the standard holley two barrel mounting pattern, which means a holley 2300 or autolite 2100 should bolt right in place of what you have now, since it is a holley 2300. you can get the carb from most any ford V8 with a two barrel carb, i suggest something like a C-code 289, or a 302 powered mustang ll or maverick.
If you have made improvements, it may need different jets. At least this means he will make sure it is running well and the choke is adjusted when it is back together.
this is true. it is important to match the fuel flow to what the engine needs. otherwise you get too much or too little fuel, in the case of the old inline six too much fuel with the two barrel conversion, and performance and fuel economy suffer.
do you need premium? does the engine detonate under load? if not then dont. only run higher octane fuels if you need them, otherwise they are a waste of money.
Also is it ok to get an alignment at a regular place like tires plus? I will be getting tires and they usually offer a deal if you get a package.
as long as the techs know what they are doing, then yes, get the wheel alignment where ever you like. you may have to supply them with the specs you want though.