wheels and tires for 78 c10

[killerspoons]

I'm 17 years old and building a 78 c10 for a school project. I'm looking at getting new wheels and tires. im keeping the stock wagon wheels for winter tires but I would like to get 20" rims for the summer and i'm wondering what size tires and the offset i'll need. I was looking at getting 275/45/20 all around but i'm not sure if they will work on the front. I would like to slowly turn this truck into something that handles well but my budget only allows for a little at a time so i'm looking at lowering it 2.5" front and 5" rear with sway bars all around and wise tires. All i'm looking to get is the widest tires i could fit on all 4 corners?