You don't actually need 8 speeds, and in my case the front der worked perfectly. I kept the biopace 52T and don't really notice it's so different.

Here's my setup from a similar-era bike, with a 600 SIS rear der.
- used RSX 7-spd brifters from ebay. These go for ~$90 for a pair in nice condition
- A 13-28 7-spd Shimano hyperglide freewheel from Harris Cyclery (they apparently don't make the 11-28 that I have) for $20
- A 38T, 130BCD Sugino chainring from Harris Cyclery for $27
- cable set for maybe $30
- total cost around $200

I don't think the 52x11 is particularly useful, and wish I had the 52x13. This is great realistic gearing for flats and hills, and you'll be amazed at how much better shifting will be with these components.