I think the injector size is different from 305 to a 350....I know for sure the sizes are different from a 4.3 to a 350....I have done that 305 to 350 swap a bunch...

Denny..... on that van did you change the ecm or the prom chip....I have a 89 Astro with a 4.3 that I have a 350 crate motor (for 89 truck) I plan to install in the van....I also have the ECM that I was just going to swap proms....?