First off...
jetstream!!
Swift is right, Richard does not do email. I think the guys a Lotus Supplies do but I'd call them anyway.
I have a pre space frame Spyder frame that is very similar to what Lotus Supplies sells. I like it but I think europa88 is right that Spyder can probably cater more specifically to your engine swap. That is a supposition so I'd call both places and discuss what you're wanting to do with them.
Have you made a decision on which motor you want to use. Probably the most popular swap is a Zetec. That means that you'll probably get the most support from frame builders and accessory vendors. For example, Dunnell has made a beautiful set of headers for a buddy of mine. I'd imagine he can provide them for you easily.
I know I speak for everybody here when I say we'd love to see some pictures of your baby - for that matter, we'd all like to track your progress as you restore her!
Good luck!