Tubby.....It is possible, with a cutting torch and welding machine anything is possible, lol, just kidding. I've never seen an S10 up close with a 454 but I have seen them on the net. Here is a link to one:
<a href="http://www.geocities.com/tasmin468/ProstreetS10.html" target="_blank">http://www.geocities.com/tasmin468/ProstreetS10.html</a>
You might want to also check out the S series WebRing where you will find lots of sites about S10's with V8's. Below is the link to that site:
<a href="http://c.webring.com/hub?ring=v8s10&list" target="_blank">http://c.webring.com/hub?ring=v8s10&list</a>
Sure hope this helps you out, Good luck and have fun.....HRS10