piece-of-cheese,
I have been using several opencores projects. And for the most part,
I've been quite pleased. In general, there are two types of interfaces
you'll find: (1) wishbone, (2) generic ... neither of which will provide
any ptf (or avalon support for that matter). You'll have to add the
blocks to your system via an interface to user logic.
WRT wishbone: I tried a few times to replace the wishbone interface with
an avalon interface ... and eventually decided it was quicker (and more
maintainable) to just insert a wishbone-to-avalon bridge.
If it's generic (e.g. like the crypto cores for example), you can just
write your own avalon wrapper.
Regards,
--Scott