Good luck finding a "spider" injection unit for that. The sequential "Vortec" units are available, but my friend with the older, batch-fire job couldn't get a suitable replacement.
There appear to be various rebuilt and refurbished spiders available for them on eBay and such, but they are proud of them. No telling about the quality either, without further research. The OP doesn't appear to be worried about the "cool factor" of keeping the CPI system and intake, so the TBI mods that have been suggested would probably be more cost effective, especially with treasure yard parts.