Welcome aboard!
Step number one is decide what you want tell car to be and work back from there. Is it for drag strips? Street use? Is gas mileage any concern at all?
Right now is the time to plan a final tranmission/rear gear/wheel&tire combo. Lots of guys just toss stuff together - oh, thays a strong trans... oh I hear lower (numerically higher) gears are good... oh I like the 'look' of those size tires.... the reality is all those things need to work together for the best results.
Then they wind up with a car that spends most of its driving time outside the optimal power band for that particular setup and complain about not enough power and horrible mileage.
Find the casting numbers and learn what you've got in the motor. Typically those poncho motors are torque monsters. Late 70s, say 77/78 TAs with w72 and the 400 used some of the biggest factory qjets of the era. So start with trying to figure out what you've got, then find a similar dyno to get an idea of power bands, use an online calculator couning your tire size to find which trans and rear combo places you comfortably in the power band at the speeds you want to run.
Also, I notice you have no wheelwells in there. I'd make a list of what else is missing on the car to start gathering for when you really start doing work.
Definitely street use. The car was mostly stripped for racing. As you noticed the wheel wells were removed along with the center console, gauges where air controls would be, has fuel cell, and the battery was put in the trunk. Battery kinda sketches me out being in an enclosed area with gas fumes. Should it stay, or should I move it back up front? I do want wheel wells back for sure since it'll be on the road a lot, and then I could put the battery up front. I'd either want a complete center console back with oil temp and pressure in a console race pod (
shown here,) or invest in a rally cluster and 'delete panels' for air controls+radio and a decent looking boot to go over the shifter.
Gas mileage isn't too much of a concern since I'm not burning anything above 93 octane.. yet. The block is a either a 75 or 76 with 6x heads.
When I put the short mufflers on I have and change the oil in a few weeks or so, I'll see what trans I have and decide what I want to do from there. I'm a broke college student, so I'm in no hurry to do anything other than get the trans rebuilt and prevent rust from spreading.
I don't consider it road worthy yet, even if it had a fully working trans. Today I got a surprise when the braided fuel hose touched a post on the alternator. I think I'll be replacing all of the hoses, rerouting brake lines away from the exhaust manifolds, and wrapping the exhaust manifolds in the near future. Oil filter is about 3/8" from the exhaust too. I start to see why a big block isn't extremely common in a gbody, but it'll be worth it in the end