It’s never a bad idea to upgrade your intake manifold during the course of a rebuild or engine swap. The stock GSLSE intake manifolds flow poorly compared to later ones, and I usually estimate a solid 10-15hp increase with an 86+ intake swap on an early engine. When doing this swap, emissions and controls are usually left off, however cruise can be retained with fabrication of a custom bracket. A custom intake must be fabricated, and small changes made here and there. Your stock wiring harness and fuel injectors/rails/afm are reused. This cleans up the engine quite a bit, while producing more power all around. Here are pics of a conversion performed using 86-88 manifolds.