Can a 5.7 spider intake manifold fit a 5.3 vortec?

No, a 5.7 spider intake manifold is not directly compatible with a 5.3 Vortec engine due to differences in design and bolt patterns. The 5.3 Vortec typically has a different intake port shape and alignment compared to the 5.7. However, with modifications and the right adapter plates, it may be possible to make them work together, but it's not a straightforward swap. Always consult an expert or do thorough research before proceeding with such modifications.