cloning long mRNAs

[Molecular Neurobiology]

Provided that a full length of surprizingly-long 25kb mRNA needs to be cloned and that sequence of only 
5kb at the 3'end is so far available, what kind of methods would you suggest?  I could suggest long-range 
5'RACE, inverse PCR, the Clontech's CAP kit as well as classical cloning using random or specific primer 
libraries.   Any suggestions or comments would be appreciated.