1989 Chevrolet Blazer Chevy K 5 Blazer 350 V8 Oil Pressure Gauge Acting Fool

I have a 1989 Chevy K-5 Blazer, 350 V8. The oil pressure gauge is acting a fool, bounces high then low and back. I want to install after market mechanical gauges, but am unsure of the effects it will have on the computer. All that I've heard is no problem . So, can you guys tell me if it will cause any problems installing the gauges and doing away with the electric ones? Thanks ever so much, Jimmy Elder