TBH...do a web search for LT1 carb conversion and you'll turn up a lot of hits. Pay particular attention on blocking off the opti and running a LT1 style radiator.
I would think originally your 85 brougham ran some form of CCC carb and HEI distributor meaning all the wiring is there to hook up the starter, distributor and alternator. One issue I see but minor is that the battery cables put the battery on the passenger side which Ponco and iirc Olds did that. Idk what engine was original to the car but Poncho engines did have the starter on the driver's side, too when everything else had them on the passenger side which is another minor set back for extending wiring. I think every other GM make had the dizzy in the rear, Buicks had the distributor in the front of the engine but with the absence of the fuel line on the driver's side, that tells me not a buick, so dizzy wires should be close vicinity to where you need them.