I currently have an 87 GTA MAF setup with no engine bad harness and have the option of buying a complete 350 with intake harness ecm from a 1990 GTA MAP setup. Is this too much of a job to get working or will this harness clip into my gauges and fan harness the same?

YES it is alot of work...

If you do not change the whole dash with harness from the 1990 MAP car you will have to repin the connectors under the dash and the bulkhead conector in the firewall.

Im in the process of doing something simlar except im changing from SD to MAF. I had to change out the dash because the repinning was to complicated for me to even try to figure out..

but hey if you good that that electronic stuff go for it.

I dont get it, all the sensor for gauges are doing is giving a signal for temp fuel, speed and rpms, its just a regular dash not digital.
When looking up info about this topic, I read people changing the actual MAF harness to MAP, Im getting the engine with intake MAP harness and ecm.
By this your saying I need to change the dash harness as well?
Im new to this so plz bare with me.