Is there any evidence that spironolactone or finasteride therapy increase blood levels of testosterone?  

Yes. It seems that both medications can do this at least in the short term. Spironolactone's effect may be more temporary.For spironolactone, an older article: Tidd et al., PMID 152681For finasteride: Stanczyk et al., PMID 23474436

Finasteride and dutasteride block 5-alpha reductase, the enzyme that converts testosterone to dihydrotestosterone. As one might expect, serum testosterone increases, but only modestly (10-20%) in cis-men. Amory et al., PMID 17299062 Spironolactone has minimal, if any effects, on serum testosterone...