So long story short, I have 1961 morris mini.

I'm putting in a b16a1 into the car.

Parts I have
b16 motor, and engine side harness obd0
socketed pr3 ecu that worked with the motor previously.

I also have:
a complete engine harness from a 94 civic(non-vtec).
a chassis side wiring harness for a 94 civic(non-vtec).
instrument cluster from the 94 civic
P30 ecu obd1
s80 hydraulic transmission(with lsd) with speed sensor and reverse sensor.
header with only one port for o2 sensor.

I was told originally it made more sense to go obd1, as there are more tuning options.
However, from the cost side, it looks like I'll need a obd1 distributor($200+), a 4 wire o2 sensor($60), different fuel injectors($275+). It still looks like I'd need more wiring harnesses built or customized.
Because I'm a honda newb, I'm hoping you can help develop a gameplan that makes sense.

Why do I want to go obd1, and what more do I need for parts/harnesses?

What if I wanted to go obd0, would I be screwing myself in the long run? What would I need to get the car running on obd0?

The car is caged and intended as a hobby racer. Even the least powerful version of software running the b16 will be a huge improvement over the old motor. However, you can never have too much power.
I'm leaning towards obd0 even though it may not be the wisest choice for tuning in the future.
Thanks for your help

 

check this out https://honda-tech.com/zerothread/2396244

 

My cousin did this except a OBD1 B16 into his 1969 mini.