The 1987 Buick Grand National originally came with a turbocharged 3.8 L V6. However this Grand National found on Bring a Trailer is powered by a turbocharged 427 ci LSx V8. The V8 motor features a Dart 427 ci LSX block, Frankenstein M311 heads, custom exhaust headers, Bullseye Power 88mm turbocharger, and Precision Turbo wastegate. The motor is controlled by a Fueltech 600 ECU and runs on either 93 octane or E85 fuel. The turbocharged V8 is backed by a Pro Torque Pro Drive Series 4L80E four-speed automatic transmission and TRZ Motorsports 9-inch rear end. The car rides on a Ridetech TruTurn front suspension with HQ-series adjustable coilovers, and manual steering box. The rear suspension uses Strange double-adjustable coilovers and TRZ sway bar. Braking is handled by Wilwood six-piston brakes in front and Strange disc brakes in back. Those are covered by BC Forged 18-inch wheels wearing Continental ExtremeContact Sport tires in front and Mickey Thompson ET Street S/S 275-series tires in back.
Source: Bring a Trailer
Ugh.
Just no.
A Grand National needs a turbo V6.
If you want a V8 G-body, use a regular Regal, or a Monte Carlo, Grand Prix, or Cutlass Supreme.