Ecu Conversion Harness

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My 89 crx si still needs a b18a engine transplant. I can get a b18a out of a 92-93 teg for about $3-$400 with 87000 miles. but since this is obd1 i have to convert my car. Now i saw hasport and another company sells ecu conversion harnesses. Is this all i will need to make my car accept this obd1 engine and everything else will plug right in? or is it still a lot more complicated. I'm trying to do this myself because i want to know my car front to back. any info would be great. should i just save a little more and have some other company do the swap for me? do you know a site that will show me how to wire this engine?

leave the engine obd0, just get a dizzy and injectors out of a 90-91 b18a... it'll be a way cheaper and easier route than buying a $200 harness and playing the obd game.
I'm doing much of the same swap and no there are (I believe) several things you still need to attend to. The easiest is a 4 wire O2 sensor. OBDI uses one but your Si is a single wire O2 sensor, so you have to wire that. Also the teg distributor has a single plug but your Rex has two distributor plugs, so you have to get a donor plug (female) and graft the wires from the Rex's distributor to the donor plug so you plug it into the new distributor.

Research carefully. Besides the motor mounts, shift linkage (if you go HASport) and maybe special A/C bracket, little stuff like this can really slow a swap down.

Best of luck.