Good Motor for D50 Swap???

Just trying to get some ideas...I have an 88 D50 sitting at the house with a blown motor. I've been thinking of building a mini out of it for my dad. I'm thinking of going for all out performance...something to give the imports a run for their money. I'm wondering what would be a good swap? I don't want to go with a 350 cause I'm looking for a well balanced well performing truck. Something that will take the hills and corners like a champ...Post up with your thoughts...