If you think that selenium toner will not produce enough intensification you can try using a chromium intensifier on the negative. I would suggest that you read up on this process before you try it. If the negative has been improperly fixed or washed there could be problems.
A better and safer way to boost the negative contrast is to tone in selenium diluted 1+4 from stock. About 5 minutes should do it.
Also bleaching and then redeveloping, particularly in any pyrogallol developer, works very well.
[FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]