Does anyone know much about these? Basically with the pinto and other non-v8 engine kits, is the running gear unsuitable if one decided to put in a small block v8?

If its Ford running gear ie Sierra or granada, then why shouldnt it work?.

Consider most V8 7's use the same running gear. The Viento does as well. Even the LV350 with the 5.7 Chevvy in it. (Granada Diff is better for that one!)

If its a Rover V8 then most are less than 200Bhp for a 3.5 and under 300 for a 4.6 litre RV8.

If you go for a Chevvy / Ford small block then you may need a good geabox.

Pilgrim offer a Chevvy V8 version using either Jag or Granada running gear so it's possible. They sound good too.

Why ask, what have you found?

The only ones to avoid (if you want a big V8) are the ones with Cortina rear axle (Mk I Sumo).
The Mk II had Granada II rear axle with either Cortina or granada II front - that can safely take a RV8. the problems may come if you want to put a Chevy or ford V8 in that chassis [this was the issue that started the whole kit-car war].
The Mk III Sumo is Sierra or Granada III based and can safely take the larger engines.

The Jag based chassis is a different beast altogether and can take pretty much any V8 as per other fake-snakes.

Try http://www.cobraclub.com/
or speak to Anthony http://www.absolutehorsepower.co.uk/Contents3.html (who builds them)

or Dave Brookes (who builds mainly dax's)
http://www.v8cobra.com/

If all else fails you could try and get an answer from Pilgrim http://www.pilgrimcars.com/